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An Introduction to Meta-Analysis
Abstract
IntroductionIndividual studiesThe summary effectHeterogeneity of effect sizesSummary points
... where ln R i is the log response ratio for study i, n is the number of studies and w i is the weight for study i, defined as (Borenstein et al., 2009): ...
... The τ 2 parameter is considered the variance of the true effect size. As it is impossible to compute it from the entire population of the effect size, τ 2 is an estimation of the observed effect by using DerSimonian and Laird method (Borenstein et al., 2009): ...
... A fail-safe number is the number of non-significant, unpublished or missing studies that need to be added to a meta-analysis to change its results from significant to non-significant. Specifically, we used Rosenthal's method that estimates how many missing studies we would need to retrieve and incorporate in the analysis before the p-value became non-significant (Borenstein et al., 2009). ...
Soil management strategies involving the application of organic matter (OM) inputs (crop residues, green and livestock manure, slurry, digestate, compost and biochar) can increase soil carbon storage but simultaneously lead to an increase in non-CO2 greenhouse gas (GHG) emissions such as N2O. Although multiple meta-analyses have been conducted on the topic of OM input impacts on GHG, none has focused specifically on European arable soils. This study plugs this gap and can assist policymakers in steering European agriculture in a more sustainable direction. The objective of this meta-analysis was to quantify how OM inputs of different nature and quality, but also the application strategy, can mitigate soil N2O emissions in different pedoclimatic conditions in Europe. We quantitatively synthesised the results of over 50 field experiments conducted in 15 European countries. Diverse arable crops, mainly cereals, were cultivated in monoculture or in crop rotations on mineral soils. Cumulative N2O emissions were monitored during periods of 30–1070 days in treatments, which received OM inputs, alone or in combination with mineral N fertiliser; and in controls fertilised with mineral N. The overall effect of OM inputs had a slight tendency to reduce N2O emissions by 10% (n = 53). With the increasing carbon-to-nitrogen ratio of the OM inputs, this mitigation effect became more pronounced. In particular, compost and biochar significantly reduced N2O emissions by 25% (n = 6) and 33% (n = 8) respectively. However, their effect strongly depended on pedoclimatic characteristics. Regarding the other types of OM inputs studied, a slight N2O emission reduction can be achieved by their application alone, without mineral N fertiliser (by 16%, n = 17). In contrast, their co-application with mineral N fertiliser elevated emissions to some extent compared to the control (by 14%, n = 22). We conclude that amongst the seven OM inputs studied, the application of compost and biochar are the most promising soil management practices, clearly demonstrating N2O emission reduction compared to mineral N fertiliser. In contrast, other OM inputs had a small tendency to mitigate N2O emissions only when applied without mineral N fertiliser.
... The presence of heterogeneity was evaluated through Cochran's Q statistic (chi-square test), which was considered significant when p ≤ 0.05 [39]. Additionally, the I 2 statistic was used to measure the percentage of variation attributed to heterogeneity [40]. ...
... Meta-regression analyses were performed to test the effects of 3-NOP doses, periods of 3-NOP supplementation, and the amount of concentrate included in the diets on the heterogeneity detected in the response variables. The method of moments proposed by Der-Simonian and Laird [38] was used in the meta-regression analyses since, according to Borenstein et al. [39], this method is well established for estimating the variance between studies. The response variables had to meet the following requirements to be evaluated with meta-regression analysis: (1) have I 2 > 50% and p < 0.05 in the Q test [39,45]; and (2) have p > 0.05 in the Egger regression asymmetry and Begg's adjusted rank correlation tests [43,44]. ...
... The method of moments proposed by Der-Simonian and Laird [38] was used in the meta-regression analyses since, according to Borenstein et al. [39], this method is well established for estimating the variance between studies. The response variables had to meet the following requirements to be evaluated with meta-regression analysis: (1) have I 2 > 50% and p < 0.05 in the Q test [39,45]; and (2) have p > 0.05 in the Egger regression asymmetry and Begg's adjusted rank correlation tests [43,44]. Covariates were divided as follows: (1) 3-NOP doses 35-100 and 101-280 mg/kg DM; (2) 3-NOP supplementation period ≤ 60 and >60 days; and (3) amount of concentrate included in the diet ≤ 700 and >700 g/kg DM. ...
This study aimed to evaluate the effects of dietary supplementation with 3-nitrooxypropanol (3-NOP) on growth performance, ruminal fermentation, and enteric methane emissions of beef cattle using a meta-analytic approach. The final meta-analysis database included results from 15 scientific articles. The response variables were analyzed through random effects models, where the results were reported as weighted mean differences (WMD) between the treatments without 3-NOP and those supplemented with 3-NOP. The dietary inclusion of 3-NOP decreased (p < 0.001) dry matter intake but did not affect (p > 0.05) average daily gain and increased (p < 0.05) feed efficiency. In the rumen, 3-NOP supplementation increased (p < 0.01) the pH and ruminal concentration of propionate, butyrate, valerate, isobutyrate, and isovalerate. In contrast, dietary supplementation with 3-NOP decreased (p < 0.001) the rumen concentration of ammonia nitrogen, total volatile fatty acids, acetate, and the acetate/propionate ratio. Furthermore, daily methane (CH 4) emission, CH 4 yield, and CH 4 emission as a percentage of gross energy ingested decreased (p < 0.001) in response to 3-NOP dietary supplementation. In conclusion, dietary supplementation with 3-nitrooxypropanol can be used as a nutritional strategy to improve feed efficiency and ruminal fermentation in beef cattle and, at the same time, reduce enteric methane emissions.
... The reliability coefficient, which is the correlation coefficient, is not suitable for meta-analysis, because the variance depends on correlation. Therefore, it can be combined by transforming and then transforming to a reliability coefficient again (Borenstein et al., 2009;. The reliability coefficients obtained in the study were transformed into Fisher's z statistics before being included in the analysis. ...
... This transformation method has been suggested in the literature and is often used by metaanalysts (Beretvas et al., 2002). Heterogeneity was examined to determine the type of model to be used in the analyses (Borenstein et al., 2009). Q statistic and its significance (Cochran, 1954), I 2 statistic (Higgins & Thomson, 2002), and τ 2 values were analyzed to examine the heterogeneity of the distributions of the studies. ...
... In the study, the α coefficient for the overall reliability of the GAAIS and the reliability generalization of the α and ω coefficients for the subscales were analyzed (Vacha-Haase, 1998). These analyses were carried out according to the random effect model since heterogeneity exists statistically and theoretically (Borenstein et al., 2009). The reliability coefficient may vary depending on the applied group (Crocker & Algina, 1986). ...
This study aims to generalize the reliability of the GAAIS, which is known to perform valid and reliable measurements, is frequently used in the literature, aims to measure one of today's popular topics, and is one of the first examples developed in the field. Within the meta-analytic reliability generalization study, moderator analyses were also conducted on some categorical and continuous variables. Cronbach's α values for the overall scale and the positive and negative subscales, and McDonald's ω coefficients for positive and negative subscales were generalized. Google Scholar, WOS, Taylor & Francis, Science Direct, and EBSCO databases were searched to obtain primary studies. As a result of the screening, 132 studies were found, and these studies were reviewed according to the inclusion criteria. Reliability coefficients obtained from 19 studies that met the criteria were included in the meta-analysis. While meta-analytic reliability generalization was performed according to the random effects model, moderator analyses were performed according to the mixed effect model based on both categorical variables and continuous variables. As a result of the research pooled, Cronbach's α was 0.881, 0.828, and 0.863 for total, the negative, and positive subscales respectively. Also, McDonald's ω was 0.873 and 0.923 for negative and positive subscales respectively. It was found that there were no significant differences between the reliability coefficients for all categorical variables. On the other hand, all continuous moderator variables (mean age, standard deviation age, and rate of female) had a significant effect.
... However, because most of the included studies did not report the mean difference and standard deviation for sexual function outcomes in yoga and control groups, we requested the information from the corresponding authors. In case of a negative response from the corresponding authors, we calculated the mean difference as postintervention mean value minus baseline mean value, and the standard deviation of the mean difference was determined using the following equation [52]: ...
... For this equation, we used three r values (0.5, 0.7, and 0.9) for sexual function outcomes in yoga and control groups [52]. These calculations are recommended for performing a meta-analysis of change scores when continuous data are missing [53]. ...
Background: Yoga practice can increase blood flow in the genital area, increase muscular strength, and improve body perception, which is related to sexual function. This study aimed to summarize the available evidence about the effects of yoga on sexual function in adults. Methods: Systematic searches of five databases were conducted from inception to April 28, with the last update on September 28, 2023. Randomized clinical trials (RCTs) that compared yoga with nonintervention control groups on sexual function in adults. Risk of bias and certainty of evidence were assessed by the Cochrane risk of bias tool 2, and the GRADE approach, respectively. Summary effect size measures were calculated using a random effects model estimation and are reported as standardized mean differences and 95% confidence intervals. Reporting followed the PRISMA guidelines. Results: Ten RCTs that comprised 730 adults (range mean age, 26.64-68.2 years; 680 [93.2 %] women) were included. For the primary outcome, yoga intervention was associated with a significant small improvement in sexual function (−0.31; −0.47 to −0.15, p = 0.0002), with some concerns about risk of bias in nine RCTs (90%) and low-certainty evidence. Subgroup analyses revealed that yoga interventions performed by women (−0.36; −0.52 to −0.21, p < 0.00001), healthy individuals (−0.38; −0.59 to −0.16, p = 0.0006), or middle-aged individuals (−0.44; −0.63 to −0.25, p < 00001) significantly improved sexual function compared with control groups. Conclusion: Yoga was associated with a small improvement in sexual function compared with nonintervention control groups in adults. However, high-quality, larger RCTs are required to draw more definitive conclusions.
... Quantitative meta-analysis offers the promise of remedying this situation. Meta-analysis is a statistical procedure for synthesizing information from multiple studies, thereby providing more precise estimates of an effect size than any single study (Borenstein et al., 2009). In addition, meta-analysis also allows the researcher to investigate the extent to which an effect varies across studies, and if so, to test whether certain study characteristics systematically produce different results. ...
... Meta-analysis is a way to systematically synthesize evidence from multiple studies to estimate effect size more precisely than is possible in an individual study, and discover inconsistencies between studies (Borenstein et al., 2009). This practice is particularly important in a field like 5 Sprouse (2009) suggested a linking hypothesis where satiation is considered the result of an "equalization response strategy" employed by participants: they tend to balance the number of positive and negative responses. ...
Sentence acceptability judgments are often affected by a pervasive phenomenon called satiation: native speakers give increasingly higher ratings to initially degraded sentences after repeated exposure. Various studies have investigated the satiation effect experimentally, the vast majority of which focused on different types of island-violating sentences in English (sentences with illicit long-distance syntactic movements). However, mixed findings are reported regarding which types of island violations are affected by satiation and which ones are not. This article presents a meta-analysis of past experimental studies on the satiation of island effects in English, with the aim of providing accurate estimates of the rate of satiation for each type of island, testing whether different island effects show different rates of satiation, exploring potential factors that contributed to the heterogeneity in past results, and spotting possible publication bias. The meta-analysis shows that adjunct islands, the Complex NP Constraint (CNPC), subject islands, the that-trace effect, the want-for construction, and whether-islands reliably exhibit satiation, albeit at different rates. No evidence for satiation is found for the Left Branch Condition (LBC). Whether context sentences were presented in the original acceptability judgment experiments predicts the differences in the rates of satiation reported across studies. Potential publication bias is found among studies testing the CNPC and whether-islands. These meta-analytic results can be used to inform debates regarding the nature of island effects and serve as a proof of concept that meta-analysis can be a valuable tool for linguistic research.
... Cohen's (2023) study meets both criteria; it is an outlier according to the criteria from Hanson and Bussière (1998), and it also exerts undue influence on the findings because the sample size is more than ten times larger than the next largest study. Study weights are determined by the inverse of the variance (Borenstein et al., 2009), which takes into account more than just the total sample size. The study weights for the six initial studies ranged from 71 to 1,270, whereas the weight for the Cohen (2023) study was 3,135. ...
... (Helmus et al., 2024). Integrating Cohen (2023) for more information on interpreting meta-analysis results, see Borenstein et al., 2009. The effect size from Cohen (2023) was significantly lower than the meta-analytic results of the other five studies (Qchange = 24.3, ...
Objective: Review current research on risk assessment tools with individuals convicted of child sexual exploitation materials (CSEM) offenses with recommendations for use in forensic, correctional, and legal settings.
Hypotheses: Multiple tools would be defensible to use with individuals convicted of CSEM offenses.
Methods: We discuss a minimum threshold of predictive accuracy to justify using a risk tool as an improvement on the typical level of accuracy expected from unstructured professional judgment. Then beyond this minimum threshold, we offer additional considerations that researchers and practitioners can use in evaluating and selecting risk tools.
Results: We identified eight risk assessment tools with predictive accuracy research on individuals convicted of CSEM offenses: the Child Pornography Offender Risk Tool (CPORT), Risk Matrix 2000/Sex (RM2000/S), OASys Sexual Reoffending Predictor – Indecent Images (OSP/I), Static-99R, STABLE-2007, ACUTE-2007, Post Conviction Risk Assessment (PCRA), and the Level of Service Inventory – Ontario Revision (LSI-OR). We review each using the evaluation considerations.
Conclusions: The CPORT, RM2000/S, STABLE-2007, and ACUTE-2007 (in conjunction with the STABLE) are all defensible tools to use for assessing risk of any sexual recidivism or CSEM recidivism specifically. There is preliminary evidence suggesting some support for Static-99R, but it may not be the ideal choice. The OSP/I consists of a single risk factor and considers risk of CSEM recidivism among all individuals convicted of sexual offenses, not only among individuals convicted of CSEM offenses. The PCRA and LSI-OR general recidivism risk tools have some empirical support in predicting general recidivism among CSEM samples (and sexual recidivism for the PCRA), with limitations noted. The use of multiple tools may have value in assessing risk and structuring management in CSEM cases, however how they are best combined for these samples is still unclear. We expect research in this area to continue to build rapidly.
... If studies reported correlation coefficients of the relationship between interpersonal problems before treatment and the therapeutic alliance, they were directly coded in the data set. Other effect sizes or statistics (regression coefficients, t statistics, etc.) were transformed using the standard formulas from Borenstein et al. (2009), which are implemented in the R package MAc Version 1.1.1 (Del Re & Hoyt, 2018). ...
... The estimation was based on the restricted maximum likelihood method, as it seems to be superior to other estimators (Assink & Wibbelink, 2016;Viechtbauer, 2005). For all analyses, the correlation coefficients were Fisher's z-transformed and back-transformed for interpretability (Borenstein et al., 2009). Additionally, we provided Cohen's d effect sizes, where d = .20 ...
Psychotherapy is an interpersonal process of collaboration toward specified treatment goals. The therapeutic alliance is well established as an important factor of psychotherapeutic change. However, the experience of distress in social interactions, commonly referred to as interpersonal problems, might be interfering with the collaborative process during psychotherapy. This study systematically reviews the literature and obtains an estimate of the relationship between pretreatment interpersonal problems and the quality of the therapeutic alliance. Overall, 27 studies with 48 correlation coefficients were included in the final analysis. Due to the nested structure of the data, a three-level meta-analytic approach with a restricted maximum likelihood estimator was applied. Alliance assessment phase, alliance rater, alliance measure instrument, and treatment type were tested as potential moderators. Heterogeneity and publication bias test were performed. The meta-analysis showed a small, but significant negative relationship between interpersonal problems at the beginning of psychotherapy and subsequent therapeutic alliance (r = −.12, SE = .02, 95% CI [−.16, −.08], p < .001, d = −.27). Only alliance assessment phase accounted for significant variability. There were no indications for a substantial publication bias. Interpersonal problems of patients before psychotherapy are a robust predictor for lower therapeutic alliance quality, albeit a small effect size. Consequently, patients who experience interpersonal problems may face greater challenges in developing a strong alliance with their therapists, especially in early stages of the treatment.
... In this descriptive study with a sample of n = 7 and a population of 481 college students, a continuous variable and standardized mean differences were used as effect sizes to analyze the difference in reading comprehension between the control and experimental groups after the use of digital technology. A random effects model (Borenstein et al., 2009) was used as the effect size. We used the method of DerSimonian and Laird (Egger et al., 2001) to calculate the standardized mean difference, its standard error, p and the 95% confidence interval (CI). ...
... Finally, this study applies three methods to analyze publication bias (Borenstein et al., 2009 Microsoft Excel was used to classify and code the data and to generate the descriptive statistics, and Jamovi version 1.6 software was used to perform the meta-analysis. ...
... To evaluate the biological response of each species (i) and functional group (j) on HAB event, we calculated the relative change (RC) of abundance (A) from the pre-HAB period (2004-2020) to the post-HAB period (2021) with the following formulae [32]: We used Cohen's standardized measure of difference to assess the significance of effect size. An effect size greater than 1.96 in absolute value suggests that the abundance in the post-HAB year changed significantly compared with the pre-HAB period [33,34]. This threshold of 1.96 corresponds to a two-tailed significance level of p < 0.05, commonly used in hypothesis testing. ...
There has been a limited number of studies on the effects of harmful algal blooms (HABs) on natural rocky intertidal ecosystems. From mid-September to early November 2021, an unprecedented HAB caused by Karenia selliformis hit the Pacific coast of southeast Hokkaido, Japan, for the first time, causing massive mortalities among marine organisms. To clarify the immediate impacts of the HAB on the abundance of 10 rocky intertidal species in four functional groups (macroalgae, sessile invertebrates, molluscan grazers, and molluscan carnivores), we focused on two questions: (1) How did the HAB affect the abundance of each species differently at the regional scale? and (2) How did the impacts of the HAB on the abundance of each functional groups vary spatially, and was the spatial variation of the HAB impacts related to the spatial distribution of the cell density of HAB species? To study these issues, we compared census data for 17 years before the HAB and within one month after it for five shores on the southeast coast of Hokkaido. The results showed that two macroalgae species and all three molluscan grazer species declined significantly after the HAB. Moreover, the decrease in molluscan grazers was significantly correlated with cell density. These results suggest that the impacts of the HAB in southeast Hokkaido on the abundance of rocky intertidal organisms are highly variable depending on species and locality, presumably because of differences in species-specific tolerances to HAB toxins and the spatial variation in the density of the HAB organisms.
... This effect size measure is appropriate given that most studies included experimental designs which compared the spending outcomes across independent groups. In cases where means where not reported, we used other indicators (e.g., F-value, t-value, p-value, correlation coefficient r) and converted these into Hedges' g, using the formulas in Borenstein et al. (2009). ...
Over 40 years of research links cashless payment methods to increased consumer spending. Referred to as the “cashless effect,” this phenomenon has recently come under scrutiny as consumers are increasingly familiar with non-cash methods which could weaken the cashless effect, while other research challenges the robustness of the effect and questions which conditions could strengthen or weaken it. The current study contributes to reaching a consensus in this ongoing debate through a large-scale meta-analysis leveraging a meta-analytical framework that synthesizes the insights from the extant literature. Across 392 effect sizes from 71 papers, we reveal a small, but significant, cashless effect. Further, we show no evidence that cashless payment method features influence the cashless effect, while various consumption situations and contextual factors do. Specifically, the cashless effect is stronger in conspicuous consumption situations, while it is weaker in pro-social consumption situations. The results also reveal that the business cycle impacts the cashless effect, with it being stronger in periods of economic growth. Finally, the cashless effect has generally weakened over time. Our findings offer novel and actionable insights for academics, consumers, and practitioners such as retailers, charities, and policymakers interested in the effects of payment methods on consumer spending behavior.
... Therefore, it is crucial to use a sample that is large enough to accurately discriminate between Type and then to rely on the trend shown by that specific sample. We defined this 'large enough' sample size to be , and determined it to be approximately ∼ 700 per bin by statistical power analysis, which is a widely used statistical tool for sample size determination in meta-analyses (e.g., Borenstein et al. 2009;Grundler et al. 2022). In statistical power analysis, the three parameters to be set are statistical power, significance threshold, and effect size. ...
Supermassive Black Holes (SMBHs) are commonly found at the centers of massive galaxies. Estimating their masses ($M_\text{BH}$) is crucial for understanding galaxy-SMBH co-evolution. We present WISE2MBH, an efficient algorithm that uses cataloged Wide-field Infrared Survey Explorer (WISE) magnitudes to estimate total stellar mass ($M_*$) and scale this to bulge mass ($M_\text{Bulge}$), and $M_\text{BH}$, estimating the morphological type ($T_\text{Type}$) and bulge fraction ($B/T$) in the process. WISE2MBH uses scaling relations from the literature or developed in this work, providing a streamlined approach to derive these parameters. It also distinguishes QSOs from galaxies and estimates the galaxy $T_\text{Type}$ using WISE colors with a relation trained with galaxies from the 2MASS Redshift Survey. WISE2MBH performs well up to $z\sim0.5$ thanks to K-corrections in magnitudes and colors. WISE2MBH $M_\text{BH}$ estimates agree very well with those of a selected sample of local galaxies with $M_\text{BH}$ measurements or reliable estimates: a Spearman score of $\sim$0.8 and a RMSE of $\sim$0.63 were obtained. When applied to the ETHER sample at $z\leq0.5$, WISE2MBH provides $\sim$1.9 million $M_\text{BH}$ estimates (78.5\% new) and $\sim$100 thousand upper limits. The derived local black hole mass function (BHMF) is in good agreement with existing literature BHMFs. Galaxy demographic projects, including target selection for the Event Horizon Telescope, can benefit from WISE2MBH for up-to-date galaxy parameters and $M_\text{BH}$ estimates. The WISE2MBH algorithm is publicly available on GitHub.
... Variances in effect sizes were calculated using the equations specified by Borenstein et al. (2009). The variance of log odds-ratios were converted to the variance for SMD by dividing by π 2 3 . ...
Background
Capacity building may play an important role in improving classroom teachers’ and early childhood educators’ (ECE) capacity to implement physical activity and FMS interventions. Capacity building is the development of knowledge, skills, and structures to improve the capability of individuals and organisations to achieve effective health promotion. This review aimed to determine the efficacy of capacity building interventions on teachers’ and ECEs’ perceived capabilities, knowledge, and attitudes relating to physical activity and fundamental movement skills.
Methods
An exhaustive literature search of six electronic databases was conducted. Controlled, single-group pre-post studies were included if they measured the effect of a capacity building intervention on in-service or pre-service classroom teachers’ (primary or secondary) or ECEs’ physical activity or fundamental skills related perceived capabilities, knowledge, or attitudes. The effects of interventions were synthesised using random effects meta-analysis. Subgroup analysis and meta-regression was conducted to determine if the effects differed based on study design, type of teacher (ECE vs. primary school), or teacher level (pre-service vs. in-service).
Results
A total of 22 studies reporting on 25 unique samples were included in the meta-analyses. Only studies reporting on ECEs and primary school teachers were identified. Interventions most commonly included training/professional development, resources and toolkits, communities of practice, mentorships, and ongoing support. Results showed that capacity building interventions significantly improved teachers’ and ECEs’ perceived capabilities (g = 0.614, 95% CI = 0.442, 0.786), knowledge (g = 0.792 95% CI = 0.459, 1.125), and attitudes (g = 0.376 95% CI = 0.181, 0.571). The effects did not differ significantly as a function of any of the moderators examined.
Conclusion
Findings from this review provide strong support that capacity building interventions are efficacious at improving teachers’ and ECEs’ perceived capabilities, knowledge, and attitudes related to promoting physical activity and teaching fundamental movement skills. Pre-service teachers and ECEs should be provided training in physical activity and fundamental movement skills as part of their degrees, and continual professional development and capacity building should be offered to in-service teachers and ECEs to promote physical activity and fundamental movement skills in children.
... The meta-analysis has been performed by following the guidelines of Borenstein et al. (2009), first of all, the analysis was carried out using the Fisher r-to-z transformed correlation coefficient (r) as the outcome measure along with variance of sample (N): ...
Purpose
This paper aims to meta-analyze the results of the prior studies related to the relationship of human capital and financial performance in Islamic banking.
Design/methodology/approach
To examine the relationship between human capital and financial of Islamic banks, 23 empirical studies having sample of 15,607 are considered for the meta-analysis. Moreover, different measures related to financial performance including return on assets (ROA), return of equity (ROE) and Tobin’s Q have been taken as moderating for further subgroup analysis.
Findings
The results of meta-analysis reveal a positive correlation between human capital and financial performance with an effect size of 0.268. The subgroup analyses showed significant positive associations of human capital with ROA and ROE, insignificant with Tobin’s Q.
Originality/value
This study suggests Islamic banking should prioritize human capital development, maintain consistency and adopt a long-term perspective. Future research should consider context-specific factors and harmonize human capital and financial performance measurements for consensus.
... In the case of not reporting Mean±SD changes, mean change was calculated by subtracting variable values at the beginning of the intervention from the end. Also, change SD was estimated using the Equation 1 [19]: ...
Background and Objectives: Failure to thrive (FTT) is a common developmental disorder in infants. Although the improvement effect of zinc supplementation in these patients was reported in some past studies, the results were conflicting. Accordingly, this study investigates the effect of zinc supplementation on factors related to growth in infants with FTT by conducting a meta-analysis. Methods: Medline, Web of Science, and Scopus databases were comprehensively searched to find randomized controlled trials investigating the effect of zinc on growth-related factors in infants with FTT. Eligible studies were extracted after screening their relevant information. The pooled effect size was estimated as a weighted mean difference with a 95% confidence interval (CI) using the random effect model method. Results: Out of 85 reviewed papers, 4 studies were eligible to enter this review. The present meta-analysis revealed that zinc supplementation in infants with FTT led to a significant increase in weight (weighted mean difference (MD)=-0.25 kg; 95% CI, 0.02%-0.49%), weight-for-age Z-score (weighted MD=0.16; 95% CI, 0.03%, 0.28%), and height-for-age Z-score (weighted MD=0.15, 95% CI, 0.001%, 0.30%), compared to control groups. In contrast, zinc supplementation had no significant effect on height and insulin-like growth factor 1 serum level. Conclusions: The findings of the current meta-analysis indicated the effectiveness of zinc supplementation in improving the developmental status of infants with FTT; however, due to the small number of included trials, it was impossible to draw definitive conclusions, and conducting randomized controlled trials with larger sample size and higher sensitivity is needed.
... The significance of the effect was determined using 95% confidence interval (CI), p value less than .05, and the weight of each effect size was derived using the inverse of variance [11]. The heterogeneity of the included studies was assessed using Q statistics and Higgin's I2 values [12], and 95% CIs were reported to account for the bias of the heterogeneity I2, which is a point estimate in small meta-analysis studies; an I2 greater than 50% was interpreted as heterogeneity [13]. ...
Purpose: This study systematically analyzed the impact of aromatherapy on pain in individuals with diabetes. Methods: A search was performed in seven electronic databases based on the PICO-SD (Population, Intervention, Comparison, Outcome, Study Design) framework. The population (P) of interest was individuals with diabetes, and the intervention (I) included aromatherapy targeting pain reduction. The comparison (C) consisted of control groups that received no intervention, another intervention, or usual care. The outcome (O) measured was pain. The quality of the selected literature was assessed using the Joanna Briggs Institute checklist. In MIX 2.0 Pro, the pooled overall effect of pain was calculated using Hedge's g and a random-effects model, and heterogeneity was calculated using the Q statistic and Higgin's I2 values. Meta-regression and exclusion sensitivity analyses were performed.Results: Five articles and seven studies were included, showing a significant pooled overall effect of aromatherapy on diabetes-related pain (Hedge’s g = −1.83, 95% CI: −2.76 to −0.91). Meta-regression demonstrated that effectiveness in reducing pain was associated with studies conducted in West Asia, those with IRB approval, and those receiving funding. Additionally, interventions involving subjects under 60, lavender oil (vs. turpentine oil or blended oils), massage therapy (vs. topical application), fewer hours per session, and more repeated measurements (vs. pre/post measurements) were associated with pain reduction.Conclusion: Aromatherapy, especially with lavender oil, effectively manages diabetes-related pain. Short-duration massage application is also effective. A personalized selection of oil type and application method could optimize therapeutic outcomes for individuals with diabetes.
... For heterogeneity analysis, we incorporate (a) the Q test for heterogeneity (Cochran, 1954), (b) the I 2 statistic (Deeks et al., 2021;Higgins & Thompson, 2002); and (c) the τ 2 and SE τ 2 (Borenstein et al., 2009). When the value of Q is statistically significant, the distribution of ES around the mean is wider and probably heterogeneous. ...
Alexithymia refers to the difficulty in identifying and communicating feelings. The only published meta-analysis on gender differences in alexithymia is based on studies at least 20 years old. However, due to changes in gender roles in recent decades, reviewing the updated literature on this topic is needed. A meta-analysis was conducted to examine gender differences in alexithymia and its dimensions between the years 2004 and 2023. In sum, 120 studies with 145 samples (N = 88,721; M age = 33.81 and SD age = 3; 47.6 % of women) met the inclusion criteria. Results revealed a significant and small effect of gender differences in alexithymia (d = 0.22; 95 % CI [0.20, 0.24]), as well as in its two dimensions: difficulties in identifying and differentiating feeling from bodily sensations (d =-0.24; 95 % CI [0.20, 0.28]) and difficulties in describing feelings to others (d = 0.26; 95 % CI [0.20, 0.30]). A medium and statistically significant effect size was only observed in externally oriented thinking (d = 0.49; 95 % CI [0.41, 0.58]). Age-related and some cultural aspects were relevant moderators in explaining gender differences in alexithymia. The results are discussed in light of theoretical and practical implications.
... We adopted the random-effects model as the meta-analysis model due to the diverse theoretical and methodological differences across the primary studies. Unlike the fixed effect, the random-effects model assumes that the between-study variance differs for all subgroups and studies that used diverse methodologies (Borenstein et al., 2021). We also addressed the case that multiple effect sizes from a single study are more likely to be correlated, which generates invalid statistics and inaccurate inferences in hypothesis testing, by employing Huber-White (H-W) OLS in attuning the variance-covariance matrix to correct for autocorrelation within studies and for arbitrary heterogeneity. ...
Purpose
The study aims to build upon the Resource-based view of the firm (RBV) and Dynamic Capability Theory (DCT) to perform a meta-analysis on the eco-innovation/SMEs’ sustainable performance relationship.
Design/methodology/approach
Employing a psychometric meta-analytic approach with a random-effects model, the study examines a sample of 134,841 SMEs covering 99 studies and 233 study effects. Subgroup and meta-regression analysis were used to test the study`s hypotheses in Comprehensive Meta-Analysis (CMA) statistical software.
Findings
Results unveil that the average impact of eco-innovation on SMEs` sustainable performance is positively significant but moderate. Moreover, it was found that eco-process, eco-product, eco-organizational, and eco-marketing innovations positively influence SMEs’ sustainable performance, but the impact of eco-organizational innovation is the strongest. Findings further reveal that eco-innovation positively influences economic, social, and environmental performance, but its effect on social performance is the largest. Moreover, our findings reveal that contextual factors, including industry type, culture, industry intensity, global sustainable competitive index, and human development index, moderate the eco-innovation/SMEs’ sustainable performance relationship. Lastly, methodological factors, namely sampling technique, study type, and publication status, account for study-study variance.
Practical implications
Our findings imply that investing in eco-innovation is worthwhile for SMEs. Therefore, CEOs/managers of SMEs must adopt eco-innovation initiatives by establishing a sustainability vision, developing employee environmental development and training, building a stakeholder management system, and promoting employee engagement in sustainability activities.
Originality/value
The study develops a holistic conceptual framework to consolidate the distinct types of eco-innovation and their association with the sustainable performance of SMEs for the first time in this research stream, thereby resolving the anecdotal results and synthesizing the fragmented literature across culture, discipline, and contexts.
... A random-effects model was applied [19] with the correction proposed by Hartung [20]. A forest plot, including 95% confidence intervals, was created to represent numerically and graphically the individual effects of each study, as well as to display the average effect size. ...
Non-specific low back pain (NSLBP) in children and adolescents has increased in recent years, and the evidence of the physiotherapy interventions in back care needs to be updated. Our main goal was to quantify the effects of preventive physiotherapy interventions on improving behavior and knowledge related to back care and prevention of NSLBP in children and adolescents. Based on two previous meta-analyses, Cochrane Library, MEDLINE, PEDro, Web of Science, LILACS, IBECS, PsycINFO, and IME databases and several journals were searched. Two researchers independently extracted data and assessed the risk of bias in the studies using the RoB2 tool. Data were described according to PRISMA guidelines. A total of 24 studies (28 reports) were included. In the posttest, the behavior variable obtained an overall effect size of d+ = 1.48 (95%CI: 0.40 to 2.56), and the knowledge variable obtained an effect size of d+ = 1.41 (95%CI: 1.05 to 1.76). Physiotherapy has demonstrated beneficial impacts on behavior and knowledge concerning back care and to prevent NSLBP in children and adolescents. Interventions focusing on postural hygiene and exercise should be preferred, especially those that are shorter in number of weeks, more intense, and incorporate as many intervention hours as possible.
Este trabajo es la continuación del artículo sobre tamaño de efecto para diferencia de medias independientes, centrándose ahora en las diferencias de proporciones y tablas de contingencia con variables nominales y muestras independientes. La investigación estadística sobre proporciones desempeña un papel fundamental en una amplia gama de ámbitos científicos y sociales al proporcionar una valiosa comprensión sobre la distribución y la incidencia de fenómenos en una población específica. Más allá de evaluar la significación estadística de las pruebas es crucial considerar la relevancia práctica o clínica de los resultados, entendiendo la importancia del tamaño de efecto. En el caso de las proporciones, nos encontramos con una amplia variedad de estadísticos de tamaño de efecto disponibles, como el coeficiente Phi, V de Cramer, W de Cohen, Fei de Ben-Shachar, h de Cohen, riesgo relativo, odds ratio, entre otros. Esta diversidad puede generar desafíos al momento de seleccionar el estadístico más adecuado para analizar los datos. Por lo tanto, este trabajo se propone abordar esta problemática en detalle, explorando las características y aplicaciones de cada estadístico, y ofreciendo orientación sobre su selección según el contexto y los objetivos de la investigación.
Objectives
This systematic review with meta-analyses of randomised trials evaluated the preventive effects of vitamin A supplements versus placebo or no intervention on clinically important outcomes, in people of any age.
Methods
We searched different electronic databases and other resources for randomised clinical trials that had compared vitamin A supplements versus placebo or no intervention (last search 16 April 2024). We used Cochrane methodology. We used the random-effects model to calculate risk ratios (RRs), with 95% CIs. We analysed individually and cluster randomised trials separately. Our primary outcomes were mortality, adverse events and quality of life. We assessed risks of bias in the trials and used Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) to assess the certainty of the evidence.
Results
We included 120 randomised trials (1 671 672 participants); 105 trials allocated individuals and 15 allocated clusters. 92 trials included children (78 individually; 14 cluster randomised) and 28 adults (27 individually; 1 cluster randomised). 14/105 individually randomised trials (13%) and none of the cluster randomised trials were at overall low risk of bias. Vitamin A did not reduce mortality in individually randomised trials (RR 0.99, 95% CI 0.93 to 1.05; I ² =32%; p=0.19; 105 trials; moderate certainty), and this effect was not affected by the risk of bias. In individually randomised trials, vitamin A had no effect on mortality in children (RR 0.96, 95% CI 0.88 to 1.04; I ² =24%; p=0.28; 78 trials, 178 094 participants) nor in adults (RR 1.04, 95% CI 0.97 to 1.13; I ² =24%; p=0.27; 27 trials, 61 880 participants). Vitamin A reduced mortality in the cluster randomised trials (0.84, 95% CI 0.76 to 0.93; I ² =66%; p=0.0008; 15 trials, 14 in children and 1 in adults; 364 343 participants; very low certainty). No trial reported serious adverse events or quality of life. Vitamin A slightly increased bulging fontanelle of neonates and infants. We are uncertain whether vitamin A influences blindness under the conditions examined.
Conclusions
Based on moderate certainty of evidence, vitamin A had no effect on mortality in the individually randomised trials. Very low certainty evidence obtained from cluster randomised trials suggested a beneficial effect of vitamin A on mortality. If preventive vitamin A programmes are to be continued, supporting evidence should come from randomised trials allocating individuals and assessing patient-meaningful outcomes.
PROSPERO registration number
CRD42018104347.
The purpose of this study was to use meta-analysis to assess the rates of bullying victimization in the United States (US) before and during the COVID-19 pandemic. Using a systematic search of academic databases and a previous meta-analysis database, we collected studies published between 1995 and 2023. Included studies used US-based data and reported on bullying involvement rates among children/adolescents across at least two data points (years), where 1 year had to be from 2020 to 2023. Data were extracted by type of bullying, gender, race, grade level, as well as numerous study-level features. Analyses included random effects meta-analyses, meta-regressions, and moderator analysis. Findings across the 79 studies and 19,033 effect sizes indicate that reported rates of traditional bullying victimization were significantly lower during the COVID pandemic years of 2020 to 2022 compared to the pre-pandemic years (23% vs 19%). This pattern was reflected across gender, grade, and most racial/ethnic groups examined. Overall, rates of cyberbullying victimization remained similar pre-pandemic vs during COVID (16% vs 17%). However, for boys, American Indian/Alaska Native youth, Asian, multi-racial, and White youth rates of cyberbullying victimization were significantly higher during COVID compared to the pre-pandemic period, while rates were significantly lower for transgender/non-binary youth during COVID (39% vs 25%). In addition, we conducted a moderator analysis and used meta-analysis to calculate pooled rates by year. Findings inform the current state of bullying involvement in the US and have implications for school-based bullying prevention practices and policies.
Findings on the motivational and emotional effects of computerized adaptive testing (CAT) compared to nonadaptive testing (NCAT) have been heterogeneous and inconclusive so far. This meta-analysis aims to determine the specific effects of CAT better by analyzing several moderator variables related to the test, the examinee, and the test setting. To be included in the meta-analysis, studies needed to be original, correlational, quasi-experimental, or experimental studies in English, German, or Chinese, and they needed to compare CAT to NCAT regarding motivational and/or emotional states. A three-level random-effects model with motivation, negative emotion, and positive emotion as dependent variables was estimated. The risk of bias and publication bias were examined. Twenty-seven studies with a total of 190 effect sizes were analyzed. The overall effect of CAT was not significant for motivation and negative emotion and significant for positive emotion after publication bias correction. The moderator analysis showed significant moderator effects for “test speededness” on motivation and positive emotion, “instantaneous feedback on given responses” and “possibility of response revision” on positive emotion, and “average difficulty of presented items” on negative emotion. For CAT configurations, it is recommended to avoid speededness, present easy items, allow for response revision, and provide feedback.
Bu çalışmada, Türkiye’deki öğretmenlerin örgütsel mutluluklarının; cinsiyet, medeni durum, eğitim durumu, branş ve kıdem değişkenlerine göre farklılaşma düzeylerinin meta-analiz yöntemiyle incelenmesi amaçlanmıştır. Bu kapsamda yapılan literatür taramasında 2022 yılı ve öncesinde Türkiye'de üretilmiş olan ve öğretmenlerin örgütsel mutluluğunu inceleyen 63 çalışmaya ulaşılmıştır. Araştırmada belirlenen ölçütlere uygun olan 25 yayın araştırmaya dâhil edilmiş ve bu araştırmaların verileri yapılan çalışmada kullanılmıştır. Çalışmada etki büyüklüğünün hesaplanmasında “CMA-Comprehensive Meta-Analysis” yazılımından yararlanılmıştır. Çalışmada, yayın yanlılığının olup olmadığını anlamak için huni saçılım grafiği, Begg ve Mazumdar Sıra Korelasyon Testi ve Egger Doğrusal Regresyon Testi kullanılmış ve yayın yanlılığının olmadığı anlaşılmıştır. Verilerin analizinde Hedges’g katsayısı kullanılmış ve güven aralığı % 95 olarak alınmıştır. İncelenen çalışmalar heterojen özellik gösterdiğinden dolayı çalışmaların etki büyüklükleri rastgele etkiler modeline göre hesaplanmıştır. Elde edilen analizler sonucunda cinsiyet açısından erkeklerin (g=.019), medeni durum açısından evli öğretmenlerin (g=.038), eğitim durumu açısından lisansüstü mezunu olan öğretmenlerin (g=.003), branş açısından sınıf öğretmenlerinin (g=.119) ve kıdem değişkeni açısından 21 yıl ve üzeri kıdeme sahip olan öğretmenlerin (g=.115) puanlarının yüksek olduğunu göstermiş ancak bu değerlerin istatistiksel olarak anlamlı olmadığı sonucuna da ulaşılmıştır. Yapılan analizler sonucunda; yıl, yayın türü, bölge, öğretim kademesi ve çalışmada kullanılan ölçek moderatör değişkenlerinin, öğretmenlerin örgütsel mutlulukları açısından hesaplanan etki büyüklüğü değerleri üzerinde anlamlı etkiye (farklılaşmaya) neden olmadıkları belirlenmiştir.
This study aimed to evaluate the effects of intervention using graphic organizers on the cognitive and affective improvement of students with intellectual disability (ID), with learning disability (LD), without disability, and at-risk learners in Korea. A total of 49 peer-reviewed journals and dissertations for the last 20 years were included for conducting this meta-analysis. The overall effect size of intervention using a graphic organizer was .78 (d) (95% CI [.63, .94], \({\tau }^{2}\) = .28) using a random-effects model. In order of strongest to weakest effects, at-risk learners (d = 1.38), students with LD (d = 1.15), students with ID (d = .76), and students without disability (d = .52). Among student variables, there is no statistically significant difference by school level, but by school type. Among intervention variables, instruction in math (d = 1.43) and Korean (d = .96); cognitive mapping (d = 1.05); 1–19 times, 1–9 weeks, 3–5 times per week; and small-size groups were the most effective intervention conditions. While several variables showed significant subgroup differences, meta-regression analyses revealed that only group size and frequency were significant moderators after controlling for other factors. In summary, intervention using a graphic organizer was more effective for students with disability and at-risk students than it was for students without disability.
Subject relative clauses (RCs) have been shown to be acquired earlier, comprehended more accurately, and produced more easily than object RCs by children. While this subject preference is often claimed to be a universal tendency, it has largely been investigated piecemeal and with low-powered experiments. To address these issues, this meta-analysis follows an established and rigorous scientific method to test the generalizability of the subject preference in RC acquisition by evaluating the collective evidence. While the results show a significant crosslinguistic subject preference, there is a large amount of heterogeneity in the data. The manifestation of this subject preference may not be uniform across languages, depending on typological properties such as language headedness, RC headedness, and main clause similarity. The true impact of these features, however, requires research on more typologically diverse languages.
Biodiversity often helps communities resist invasion. However, it is unclear whether this diversity–invasion relationship holds true under environmental changes. Here, we conduct a meta-analysis of 1010 observations from 25 grassland studies in which plant species richness is manipulated together with one or more environmental change factors to test invasibility (measured by biomass or cover of invaders). We find that biodiversity increases resistance to invaders across various environmental conditions. However, the positive biodiversity effect on invasion resistance is strengthened under experimental warming, whereas it is weakened under experimentally imposed drought. When multiple factors are imposed simultaneously, the positive biodiversity effect is strengthened. Overall, we show that biodiversity helps grassland communities resist plant invasions under multiple environmental changes. Therefore, investment in the protection and restoration of native biodiversity is not only important for prevention of invasions under current conditions but also under continued global environmental change.
This indispensable sourcebook covers conceptual and practical issues in research design in the field of social and personality psychology. Key experts address specific methods and areas of research, contributing to a comprehensive overview of contemporary practice. This updated and expanded second edition offers current commentary on social and personality psychology, reflecting the rapid development of this dynamic area of research over the past decade. With the help of this up-to-date text, both seasoned and beginning social psychologists will be able to explore the various tools and methods available to them in their research as they craft experiments and imagine new methodological possibilities.
This indispensable sourcebook covers conceptual and practical issues in research design in the field of social and personality psychology. Key experts address specific methods and areas of research, contributing to a comprehensive overview of contemporary practice. This updated and expanded second edition offers current commentary on social and personality psychology, reflecting the rapid development of this dynamic area of research over the past decade. With the help of this up-to-date text, both seasoned and beginning social psychologists will be able to explore the various tools and methods available to them in their research as they craft experiments and imagine new methodological possibilities.
This indispensable sourcebook covers conceptual and practical issues in research design in the field of social and personality psychology. Key experts address specific methods and areas of research, contributing to a comprehensive overview of contemporary practice. This updated and expanded second edition offers current commentary on social and personality psychology, reflecting the rapid development of this dynamic area of research over the past decade. With the help of this up-to-date text, both seasoned and beginning social psychologists will be able to explore the various tools and methods available to them in their research as they craft experiments and imagine new methodological possibilities.
This meta-analysis is an investigation into anomalous perception (i.e., conscious identification of information without any conventional sensorial means). The technique used for eliciting an effect is the Ganzfeld condition (a form of sensory homogenization that eliminates distracting peripheral noise). The database consists of studies published between January 1974 and December 2020 inclusive.
The overall effect size estimated both with a frequentist and a Bayesian random-effect model, were in close agreement yielding an effect size of approximately .08 (.04 -.12). This result passed four publication bias tests and seems not contaminated by questionable research practices.
Trend analysis carried out with a cumulative meta-analysis and a meta-regression model with year of publication as a covariate, did not indicate sign of decline of this effect size.
The moderators’ analyses show that the selected participants’ effect size was almost three-times that obtained by non-selected participants and that tasks that simulate telepathic communication show a two-fold effect size for tasks requiring the participants to guess a target.
The Stage 1 Registered Report can be accessed here: https://doi.org/10.12688/f1000research.24868.3
School engagement is a multidimensional concept describing how students behave, feel, and think. Previous meta‐analyses suggest that school engagement may be underpinned by specific aspects of teacher support. However, given that school engagement is also multifaceted, it is important to examine how each aspect of school engagement is related to different aspects of teacher support. Thus, a meta‐analysis was conducted to ascertain the magnitude of the association between different domains of teacher support and various dimensions of school engagement. We also considered the moderating roles of study (e.g., study design) and sample characteristics (e.g., school level). Of the 1249 studies identified from three databases, 141 studies (i.e., 525,129 students) met the inclusion criteria. Results indicated that teacher support was positively associated with school engagement, but the magnitude of this association differed depending on which aspects of teacher support and school engagement were examined. Significant moderating effects were evident for sample language discrepancy (i.e., discrepancy between the language spoken by the student at home and in school), school level, sex, study design, and informants. Current findings emphasize a need to adopt a comprehensive approach when examining teacher support and school engagement. Findings also suggest the importance of fostering an emotionally supportive school context to promote school engagement among students. Implications for educational research and practice are discussed.
Peak alpha frequency (PAF), the dominant oscillatory frequency within the alpha range (8–12 Hz), is associated with cognitive function and several neurological conditions, including chronic pain. Manipulating PAF could offer valuable insight into the relationship between PAF and various functions and conditions, potentially providing new treatment avenues. This systematic review aimed to comprehensively synthesise effects of non‐invasive brain stimulation (NIBS) on PAF speed. Relevant studies assessing PAF pre‐ and post‐NIBS in healthy adults were identified through systematic searches of electronic databases (Embase, PubMed, PsychINFO, Scopus, The Cochrane Library) and trial registers. The Cochrane risk‐of‐bias tool was employed for assessing study quality. Quantitative analysis was conducted through pairwise meta‐analysis when possible; otherwise, qualitative synthesis was performed. The review protocol was registered with PROSPERO (CRD42020190512) and the Open Science Framework ( https://osf.io/2yaxz/ ). Eleven NIBS studies were included, all with a low risk‐of‐bias, comprising seven transcranial alternating current stimulation (tACS), three repetitive transcranial magnetic stimulation (rTMS), and one transcranial direct current stimulation (tDCS) study. Meta‐analysis of active tACS conditions (eight conditions from five studies) revealed no significant effects on PAF (mean difference [MD] = −0.12, 95% CI = −0.32 to 0.08, p = 0.24). Qualitative synthesis provided no evidence that tDCS altered PAF and moderate evidence for transient increases in PAF with 10 Hz rTMS. However, it is crucial to note that small sample sizes were used, there was substantial variation in stimulation protocols, and most studies did not specifically target PAF alteration. Further studies are needed to determine NIBS's potential for modulating PAF.
Background
While it has been examined whether there are similar magnitudes of muscle strength and hypertrophy adaptations between low-load resistance training combined with blood-flow restriction training (BFR-RT) and high-load resistance training (HL-RT), some important potential moderators (e.g., age, sex, upper and lower limbs, frequency and duration etc.) have yet to be analyzed further. Furthermore, training status, specificity of muscle strength tests (dynamic versus isometric or isokinetic) and specificity of muscle mass assessments (locations of muscle hypertrophy assessments) seem to exhibit different effects on the results of the analysis. The role of these influencing factors, therefore, remains to be elucidated.
Objectives
The aim of this meta-analysis was to compare the effects of BFR- versus HL-RT on muscle adaptations, when considering the influence of population characteristics (training status, sex and age), protocol characteristics (upper or lower limbs, duration and frequency) and test specificity.
Methods
Studies were identified through database searches based on the following inclusion criteria: (1) pre- and post-training assessment of muscular strength; (2) pre- and post-training assessment of muscular hypertrophy; (3) comparison of BFR-RT vs. HL-RT; (4) score ≥ 4 on PEDro scale; (5) means and standard deviations (or standard errors) are reported or allow estimation from graphs. In cases where the fifth criterion was not met, the data were requested directly from the authors.
Results
The main finding of the present study was that training status was an important influencing factor in the effects of BFR-RT. The trained individuals may gain greater muscle strength and hypertrophy with BFR-RT as compared to HL-RT. However, the results showed that the untrained individuals experienced similar muscle mass gains and superior muscle strength gains in with HL-RT compared to BFR-RT.
Conclusion
Compared to HL-RT, training status is an important factor influencing the effects of the BFR-RT, in which trained can obtain greater muscle strength and hypertrophy gains in BFR-RT, while untrained individuals can obtain greater strength gains and similar hypertrophy in HL-RT.
Plain language summary
Do psychological and social interventions promote improved mental health in people living in low‐ and middle‐income countries affected by humanitarian crises?
Key message
– We did not find enough evidence in favour of interventions for promoting positive aspects of mental health in humanitarian settings. Larger, well‐conducted randomised studies are needed.
Mental health during a humanitarian crisis
A humanitarian crisis is an event, or series of events, that threatens the health, safety, security, and well‐being of a community or large group of people, usually over a wide area. Examples include wars and armed conflicts; famine; and disasters triggered by hazards such as earthquakes, hurricanes, and floods. People living through a humanitarian crisis may experience physical and mental distress and experience highly challenging circumstances that make them vulnerable to developing mental disorders, such as post‐traumatic stress disorder, depression, and anxiety. The estimated occurrence of mental disorders during humanitarian crises is 17% for depression and anxiety, and 15% for post‐traumatic stress disorder.
What are psychological and social interventions?
Psychological and social interventions (also called psychosocial) recognise the importance of the social environment for shaping mental well‐being. They usually have both psychological components (related to the mental and emotional state of the person; e.g. relaxation) and social components (e.g. efforts to improve social support). They can be aimed at promoting positive aspects of mental health (e.g. strengthening hope and social support, parenting skills), or prevent and reduce psychological distress and mental disorders.
What did we want to find out?
We wanted to know if psychosocial interventions could promote positive mental health outcomes in people living through humanitarian crises in low‐ and middle‐income countries, compared with inactive comparators such as no intervention, intervention as usual (participants are allowed to seek treatments that are available in the community), or waiting list (participants receive the psychosocial intervention after a waiting phase).
What did we do?
We searched for studies that looked at the effects of psychosocial interventions on positive aspects of people's mental health in low‐ and middle‐income countries affected by humanitarian crises. In these studies, we selected those outcome measures representative of positive emotions, positive social engagement, good relationships, meaning, and accomplishment. This is in line with the definition of mental health given by the World Health Organization, according to which mental health is "a state of mental wellbeing that enables people to cope with the stresses of life, realise their abilities, learn well and work well, and contribute to their community." We looked for randomised controlled studies in which the interventions people received were decided at random. This type of study usually gives the most reliable evidence about the effects of an intervention.
What did we find?
We found 13 studies on mental health promotion with a total of 7917 participants. Nine studies were with children and adolescents (aged seven to 18 years), and four were with adults (aged over 18 years). Four studies were carried out in Lebanon; two in India; and one study each in the Democratic Republic of the Congo, Jordan, Haiti, Bosnia and Herzegovina, the occupied Palestinian Territories (oPT), Nepal, and Tanzania. The average study duration was 18 weeks (minimum 10 weeks, maximum 32 weeks). Trials were generally funded by grants from academic institutions or non‐governmental organisations. The studies measured mental well‐being, functioning, and prosocial behaviour (a behaviour that benefits other people or society as a whole), at the beginning of the study, at the end of the intervention, and three or four months later. They compared the results in people who did and did not receive the intervention.
What are the results of our review?
There is not enough evidence to make firm conclusions. In children and adolescents, psychosocial interventions may have little to no effect in improving mental well‐being, functioning, and prosocial behaviour, but the evidence is very uncertain. For the adult population, we found encouraging evidence that psychosocial interventions may improve mental well‐being slightly, but there were no data on any other positive dimensions of mental health. Overall, for both children and adults, we are not confident that these results are reliable: the results are likely to change when further evidence is available.
What are the limitations of the evidence?
The main limitation of this review is that we cannot guarantee that the evidence we have generated is trustworthy. This is a direct consequence of the small amount of data that addressed our research question. By conducting analyses from such a small pool of data, we cannot be sure that the changes in outcomes are related to the interventions provided, rather than due to the play of chance. Furthermore, people in the studies were aware of which treatment they were getting, and not all the studies provided data about everything that we were interested in.
How up to date is this evidence?
We included evidence published up to January 2023.
This study aimed to identify the effects of peer relationship instructions between students with and without disabilities in inclusive education settings in South Korea. We conducted a meta-analysis using journal articles published over the last 20 years. From a total of 1419 student data within 33 primary studies, we found an overall effect size of 0.78 (Hedges’ g), which indicates a strong effect size of intervention efforts on peer relations of students with disabilities. With respect to outcomes, we found higher effect sizes (g = 0.82) particularly on collaboration than self-directedness (g = 0.47). We also found that instructions were highly effective for both students with (g = 0.93) and without disabilities (g = 0.76). It would be encouraged for educators to put consistent effort into implementing instructions that target to improve peer relationships and consider instruction variables such as length of program while balancing the quantitative and qualitative aspects of peer relationship.
Psychological treatment for social anxiety disorder (SAD) has been found to be less effective than for other anxiety disorders. Targeting the vivid and distressing negative mental images typically experienced by individuals with social anxiety could possibly enhance treatment effectiveness. To provide both clinicians and researchers with an overview of current applications, this systematic review and meta‐analysis aimed to evaluate the possibilities and effects of imagery‐based interventions that explicitly target negative images in (sub)clinical social anxiety. Based on a prespecified literature search, we included 21 studies, of which 12 studies included individuals with a clinical diagnosis of SAD. Imagery interventions ( k = 28 intervention groups; only in adults) generally lasted one or two sessions and mostly used imagery rescripting with negative memories. Others used eye movement desensitization and reprocessing and imagery exposure with diverse intrusive images. Noncontrolled effects on social anxiety, imagery distress and imagery vividness were mostly large or medium. Meta‐analyses with studies with control groups resulted in significant medium controlled effects on social anxiety ( d = −0.50, k = 10) and imagery distress ( d = −0.64, k = 8) and a nonsignificant effect on imagery vividness. Significant controlled effects were most evident in individuals with clinically diagnosed versus subclinical social anxiety. Overall, findings suggest promising effects of sessions targeting negative mental images. Limitations of the included studies and the analyses need to be considered. Future research should examine the addition to current SAD treatments and determine the relevance of specific imagery interventions. Studies involving children and adolescents are warranted.
This chapter explores the use of statistical techniques for addressing non-stochastic properties of life cycle assessment. It includes the use of regression analysis, machine learning and meta-analysis.
Obsessive–compulsive disorder (OCD) is a common mental health condition characterized by distressing, intrusive thoughts (obsessions) and repetitive behaviours (compulsions) aimed at reducing anxiety. Internet-based cognitive behavioural therapy (ICBT) has emerged as an effective treatment modality for various mental health disorders. This meta-analysis evaluates the efficacy of guided self-help ICBT (GSH ICBT) and unguided self-help ICBT (SH ICBT) against active and passive control conditions in adults with OCD. A comprehensive systematic literature search yielded 12 randomized controlled trials (RCTs) comprising 15 comparison arms (N = 1416) that met the inclusion criteria. Results indicate that GSH ICBT significantly reduced OCD symptomatology posttreatment compared to active controls (g = 0.378, k = 9), with no significant effects maintained at follow-up (g = 0.153, k = 4). GSH ICBT was also found to be as effective as active CBT interventions in reducing comorbid anxiety and depression symptoms posttreatment (g = 0.278, k = 6) and at follow-up (g = 0.124, k = 4). However, improvements in quality of life were not significant posttreatment (g = 0.115, k = 4) nor at follow-up (g = 0.179, k = 3). Combined GSH and SH ICBT demonstrated large effects on reducing OCD symptoms (g = 0.754, k = 6), medium effects on comorbid symptoms (g = 0.547, k = 6) and small effects on quality of life (g = 0.227, k = 2) when compared to inactive controls. No significant differences were found between GSH and SH ICBT in all measured outcomes posttreatment (OCD: g = 0.098, k = 3; AD: g = 0.070, k = 3; QoL: g = −0.030, k = 1) and at follow-up (OCD: g = 0.265, k = 2; AD: g = 0.084, k = 2; QoL: g = 0.00, k = 1). Sample size was identified as a significant moderator of treatment effects. This paper further explores clinical significance, treatment adherence, therapist time investment and moderator influences of the ICBT. The limitations of the study and recommendations for future research are thoroughly discussed.
Two articles by Garenne (2023a,b) argue that voluntary medical male circumcision does not reduce human immunodeficiency virus transmission in Africa. Here we point out key evidence and analytical flaws that call into question this conclusion.
Pollinator diversity plays an important role in improving the resilience of pollination services. However, agricultural intensification is causing declines in pollinator diversity. Such losses could be mitigated and even reversed by agroforestry systems, whose structural complexity exceeds that of intensive agricultural systems. Research, primarily conducted in tropical regions, suggests that efficiently managing agroforestry systems can increase pollinator diversity.
We performed a global meta‐analysis to explore how coffee agroforestry management practices affect the diversity of bee pollinators. We employed 137 sets of results from 20 studies that had been conducted at widely distributed locations across four of the seven continents. More specifically, we investigated the impact of augmenting floral resources (60 sets of results) and shade‐tree cover (43 sets of results) and reducing the distance to natural forests (34 sets of results). Additionally, we examined key moderating factors, including climatic conditions, pollinator sociality, the metrics used to describe pollinator diversity, pollinator sampling methods, the metrics used to characterise the effects of management practices and floral resource type.
We observed that bee pollinator diversity broadly increased as local floral resources increased in tropical coffee agroforestry systems. Shade‐tree cover and proximity to natural forests did not broadly influence bee pollinator diversity. However, the strength and direction of the relationships between the agroforestry management practices and bee pollinator diversity were moderated by different factors, mainly climatic conditions and pollinator sociality.
Our findings underscore the importance of managing coffee agroforestry systems to maximise bee diversity, which is crucial for coffee plant pollination. The broader objective should be to ensure the availability of resources that promote pollinator fitness, effective pollination and, as a consequence, crop yields.
Background
Epidemiological studies regarding the correlation between anti-Müllerian hormone (AMH) and insulin resistance (IR) in polycystic ovarian syndrome (PCOS) remain inconsistent. The primary aim of this study was to determine the correlations between AMH and IR in patients with PCOS and to explore the selected factors that influence the correlations.
Methods
We conducted systemic searches of online databases (PubMed, Science Direct, Taylor and Francis, Scopus, and ProQuest) from inception to December 20, 2023 and manual searches of the associated bibliographies to identify relevant studies. We then performed subgroup and sensitivity analyses to explore the sources of heterogeneity, followed by a publication bias risk assessment of the included studies using the Joanna Briggs Institute critical appraisal tool. We used a random-effects model to estimate the pooled correlations between AMH and the homeostatic model assessment for insulin resistance (HOMA-IR) in patients with polycystic ovarian syndrome (PCOS).
Results
Of the 4835 articles identified, 22 eligible relevant studies from three regions were included and identified as low risk of bias. The random-effects pooled correlation estimate was 0.089 (95% confidence interval [CI]: −0.040, 0.215), with substantial heterogeneity (I² = 87%; τ² = 0.0475, p < .001). Subgroup analyses showed that the study region did not influence the correlation estimates, and sensitivity analysis showed no significant alteration in the pooled correlation estimate or 95% CI values. No publication bias was observed.
Conclusion
There was a weak, statistically insignificant correlation between AMH and HOMA-IR in patients with PCOS. The correlation estimates did not vary according to the study participants’ regions.
This study aimed to integrate the results of prior studies on the effectiveness of AI education in K-12 Korean classrooms to draw systematic and comprehensive conclusions. To achieve this goal, a review of 64 studies on AI education in Korea that were conducted from 2019 to 2023 was subjected to a meta-analysis. The total effect size of AI education and the effect size for each categorical variable were calculated. The results of the meta-analysis are as follows. The overall effect size of AI education is 0.897 (95%CI = 0.781 ~ 1.013, p < .05), which can be interpreted as a large effect. In terms of learning effect, the cognitive domain had a large effect, and the affective domain had a medium effect. In addition, the effect size by publication type, school grade, subject, class type, activity type, and other categories was presented. In the early stages of AI education policy, this meta-analysis presents evidence-based action recommendations by synthesizing the results of prior studies. This study provides implications for instructional design and supportive plans that can increase the effectiveness of AI education.
Choice can be driven both by rewards and stimuli that signal those rewards. Under certain conditions, pigeons will prefer options that lead to less probable reward when the reward is signaled. A recently quantified model, the Signal for Good News (SiGN) model, assumes that in the context of uncertainty, signals for a reduced delay to reward reinforce choice. The SiGN model provides an excellent fit to previous results from pigeons and the current studies are the first to test a priori quantitative predictions. Pigeons chose between a suboptimal alternative that led to signaled 20% food and an optimal alternative that led to 50% food. The duration of the choice period was manipulated across conditions in two experiments. Pigeons strongly preferred the suboptimal alternative at the shorter durations and strongly preferred the optimal alternative at the longer durations. The results from both experiments fit well with predictions from the SiGN model and show that altering the duration of the choice period has a dramatic effect in that it changes which of the two options pigeons prefer. More generally, these results suggest that the relative value of options is not fixed, but instead depends on the temporal context.
Phubbing, a pervasive social behavior linked to smartphone usage, involves users neglecting their conversation partners to engage with their phones. Despite consistent exploration of its association with the concept of Fear of Missing Out (FOMO), findings in the existing literature exhibit notable inconsistency. To address this gap, the present study employs a systematic review and meta-analysis to scrutinize the intricate relationship between phubbing behavior and FOMO. A comprehensive systematic review, spanning up to December 10, 2023, encompassed databases such as PubMed, Scopus, Web of Science, ProQuest, and Google Scholar. The resulting dataset comprised 27 eligible studies, incorporating insights from 20,415 participants across 15 countries. Rigorous evaluation of study quality was executed using the Newcastle Ottawa Scale, while statistical analyses were meticulously conducted using R Studio. Revealing a robust positive association, phubbing behavior was significantly linked to FOMO (ES = 0.43, 95% CI: 0.36, 0.49, I2: 97.5%, τ2: 0.05). Correcting for detected publication bias using the Trim & Fill method, an additional 16 studies were included, fortifying the robustness of the findings. Moderation analysis uncovered significant influences of location (p<0.01), income level (p<0.01), sampling method (p<0.01), phubbing scale (p<0.01), and FOMO scale and type (p<0.01) on the estimated relationship. Univariate meta-regression highlighted the substantial impact of sample size (R2 = 11.81%, p <0.01), while multivariate meta-regression illuminated the combined effects of publication year, study quality score, sample size, mean age, and female proportion on the estimated relationship (k = 19, R2 = 52.85%, I2 = 93.78%, p <0.05). Furthermore, post-hoc influential analysis, conducted through the leave-one-out method, offered additional depth to the examination.
Background
Long-term static stretching as well as foam rolling training can increase a joint’s range of motion (ROM). However, to date, it is not clear which method is the most effective for increasing ROM.
Objective
The purpose of this systematic review and meta-analysis was to compare the effects of static stretching and foam rolling training on ROM.
Methods
The literature search was performed in PubMed, Scopus, and Web of Science to find the eligible studies. Eighty-five studies (72 on static stretching; and 13 on foam rolling) were found to be eligible with 204 effect sizes (ESs). For the main analyses, a random-effect meta-analysis was applied. To assess the difference between static stretching and foam rolling, subgroup analyses with a mixed-effect model were applied. Moderating variables were sex, total intervention duration, and weeks of intervention.
Results
Static stretch (ES = − 1.006; p < 0.001), as well as foam rolling training (ES = − 0.729; p = 0.001), can increase joint ROM with a moderate magnitude compared with a control condition. However, we did not detect a significant difference between the two conditions in the subgroup analysis (p = 0.228). When the intervention duration was ≤ 4 weeks, however, a significant change in ROM was shown following static stretching (ES = − 1.436; p < 0.001), but not following foam rolling (ES = − 0.229; p = 0.248). Thus, a subgroup analysis indicated a significant favorable effect with static stretching for increasing ROM compared with foam rolling (p < 0.001) over a shorter term (≤ 4 weeks). Other moderator analyses showed no significant difference between static stretch and foam rolling training on ROM.
Conclusions
According to the results, both static stretching and foam rolling training can be similarly recommended to increase joint ROM, unless the training is scheduled for ≤ 4 weeks, in which case static stretching demonstrates a significant advantage. More studies are needed with a high-volume foam rolling training approach as well as foam rolling training in exclusively female participants.
Nasopharyngeal carcinoma is a significant health challenge that is particularly prevalent in Southeast Asia and North Africa. MRI is the preferred diagnostic tool for NPC due to its superior soft tissue contrast. The accurate segmentation of NPC in MRI is crucial for effective treatment planning and prognosis. We conducted a search across PubMed, Embase, and Web of Science from inception up to 20 March 2024, adhering to the PRISMA 2020 guidelines. Eligibility criteria focused on studies utilizing DL for NPC segmentation in adults via MRI. Data extraction and meta-analysis were conducted to evaluate the performance of DL models, primarily measured by Dice scores. We assessed methodological quality using the CLAIM and QUADAS-2 tools, and statistical analysis was performed using random effects models. The analysis incorporated 17 studies, demonstrating a pooled Dice score of 78% for DL models (95% confidence interval: 74% to 83%), indicating a moderate to high segmentation accuracy by DL models. Significant heterogeneity and publication bias were observed among the included studies. Our findings reveal that DL models, particularly convolutional neural networks, offer moderately accurate NPC segmentation in MRI. This advancement holds the potential for enhancing NPC management, necessitating further research toward integration into clinical practice.
In recent years, our increasing use of technology has resulted in the production of vast amounts of data. Consequently, many researchers have analyzed digital data in attempt to understand its relationship with individuals’ personalities. Such endeavors have inspired efforts from divergent fields, resulting in widely dispersed findings that are seldom synthesized. In this two-part study, we draw from two distinct areas of personality prediction across psychology and computer science to explore the convergent validity of self-reports with human perception and machine learning algorithms, the identifiability of the Big Five traits, and the predictability of different types of data. In Study 1, five meta-analyses of human perception studies integrating findings from 24,124 individuals rated across 30 independent samples demonstrated moderate convergent validity across all traits (ranging from ρ = 0.38 for Neuroticism, to ρ = 0.57 for Openness). In Study 2, a multilevel meta-analysis of computer prediction studies reporting 534 effect sizes across 42 studies also demonstrated moderate convergent validity (ρ = 0.30). Multivariate analyses of the significant moderators highlighted that X, Facebook, Sina Weibo, videos, and smartphones had a negative impact on the variance identified. Finally, in synthesizing the extant literature, we discuss the measures used to assess personality and the analytical approaches adopted. We identify the strengths and limitations across each field and explain how interdisciplinary methodologies could advance the testing and development of psychological theory.
It is well recognized that children born preterm have specific learning difficulties. The objective of this study is to carry out a systematic review and meta-analysis on preterm children's reading ability performance. Of the 486 studies identified, 53 met the inclusion criteria, resulting in 143 effect sizes. 33,500 children between 5 and 18 years were included of whom 13,765 were preterm infants and 19,735 were full-term infants. Among preterm-born children without neurodevelopmental disorders significant differences and larger effect sizes were found in the reading subcategories, letter-word knowledge, reading comprehension, and spelling, whereas no significant differences were found in phonological awareness and rapid automatized naming. Extremely preterm children showed larger effect size. The present meta-analysis, which includes a much larger number of studies, shows that preterm children have lower performance than full-term children in reading and spelling. This fact underlines the need to design, develop and implement neuroeducational programs that take into account the characteristics of preterm born students.
English
The International Campbell Collaboration (C2) prepares, maintains and disseminates high-quality systematic reviews in the social, behavioural and educational sciences. As part of its effort to ensure that systematic reviews are based on a set of systematic, transparent and replicable procedures, C2 has produced a set of policy briefs. One of these, the C2 Information retrieval policy brief , proposes policies for searching the literature for C2 reviews, addresses key issues and challenges faced by C2 reviewers, and recommends working with an information specialist (IS). This article illustrates how the information retrieval issues raised in the brief have been addressed by one C2 review team, through the inclusion of an IS as an integral member of its review team. This unique approach recognises that information retrieval is a continuous and important process, requiring the ongoing expertise of a professional. Cost implications for the provision of ongoing support by an IS are briefly addressed, along with various alternative approaches.
Quantitative research synthesis usually involves the combination of estimates of the standardized mean difference (effect size) derived from independent research studies. In some cases, effect size estimates are available only if the difference between experimental and control group means is statistically significant. If the quantitative result of a study is observed only when the mean difference is statistically significant, the observed mean difference, variance, and effect size are biased estimators of the corresponding population parameters. The exact distribution of the sample effect size is derived for the case in which only studies yielding statistically significant results may be observed. The maximum likelihood estimator of effect size also is derived under the model in which only significant results are observed. The exact distribution of the maximum likelihood estimator is obtained numerically and is used to study the bias of the maximum likelihood estimator. An empirical sampling study is used to supplement the analytic results.
Meta-analysis is a relatively new discipline whose techniques are unfamiliar to many physicians. A meta-analysis should combine the careful thought and synthesis of a good review with the scientific rigor of a good experiment. In the report of a meta-analysis, the data from the combined studies should be displayed so that clinicians can see at a glance the spectrum of results. The justification for combining the results and the sensitivity to underlying assumptions must be made clear. Regardless of the summary number, meta-analyses should shed light on why trials differ, raise research and editorial standards by calling attention to the strengths and weaknesses of the body of research in an area, and provide an objective view of what the research literature says. When a sufficient number of similar studies addresses a topic, a meta-analysis may indicate a quantitative 'truth'; however, the computing of weighted averages is a comparatively small part of the process and should not be seen as its most important contribution.
Statistical tests are often used to compare two or more groups. When the tests show "no significant difference," many authors/readers conclude that this means that the groups are identical. Often this outcome is merely the result of inadequate sample size. The adequacy of sample size depends on well established mathematical principles, not on the investigator's intuition. The real meaning of "no significant difference" is discussed.
Three hundred thirty-five published articles from six medical journals that contained "negative" results were examined to determine the probability of detecting "small," "medium," and "large" therapeutic improvements. The mean probability of detecting a small effect size was.138; for a medium effect size, the probability was.387; and for a large effect size, it was.614.
(Arch Intern Med 1981;141-1307-1310)
The use of randomized control trials to assess the usefulness of therapeutic drugs over the last half century has brought significant benefits to patient care. The full potential benefits, however, have been only partially fulfilled because available data are frequently poorly used. Meta-analysis has emerged as an important tool for combining clinical evidence. Several examples are presented that compared the results of cumulative meta-analysis of randomized control trials with clinical expert recommendations. These comparisons demonstrated that clinical expert recommendations are often not synchronized with accumulating evidence, and this lack of recognition often resulted in delays in the acceptance of effective drugs and the slow abandonment of possibly harmful therapeutic practices. The problems of inappropriate therapeutic drug use will only intensify as new drugs are introduced and new uses for established drugs are proposed. The rational use of therapeutic drugs can be achieved only through the routine use of meta-analysis on high-quality clinical data. Some suggestions are made to improve the quality of the original research and the ways of assembling meta-analyses and disseminating their results.
A statistical wit once remarked that researchers often pose the wrong question and then proceed to answer that question incorrectly. The question that researchers intend to ask is whether or not a treatment effect is clinically significant. The question that is typically asked, however, is whether or not the treatment effect is statistically significant--a question that may be only marginally related to the issue of clinical impact. Similarly, the response, in the form of a p value, is typically assumed to reflect clinical significance but in fact reflects statistical significance. In an attempt to address this problem the medical literature over the past decade has been moving away from tests of significance and toward the use of confidence intervals. Concretely, study reports are moving away from "the difference was significant with a p value under 0.01" and toward "the one-year survival rate was increased by 20 percentage points with a 95% confidence interval of 15 to 24 percentage points." By focusing on what the effect is rather than on what the effect is not confidence intervals offer an appropriate framework for reporting the results of clinical trials. This paper offers a non-technical introduction to confidence intervals, shows how the confidence intervals framework offers advantages over hypothesis testing, and highlights some of the controversy that has developed around the application of this method. Additionally, we make the argument that studies which will be reported in terms of confidence intervals should similarly be planned with reference to confidence intervals. The sample size should be set to ensure that the estimates of effect size will be reported not only with adequate power but also with appropriate precision.
Despite its growing role in survey research, the telephone survey has been largely neglected with respect to the design and
testing of statistical procedures for assuring response privacy (e.g., randomized response techniques). This paper demonstrates
that such procedures are no less feasible to administer in telephone surveys than in face-to-face surveys. Both randomized
response techniques and alternatives to randomized response are considered.
There is debate on the role of male circumcision in HIV transmission. Most case-control and cohort studies from Africa have shown an association between a lack of circumcision and an increased risk of HIV infection in men. The evidence is conflicting, however, with cross-sectional surveys from Tanzania and Rwanda either showing no relationship or an association in the opposite direction. A recent review and meta-analysis of the literature concluded that the risk of HIV infection was lower in uncircumcised men (combined odds ratio 0.94, 95% confidence interval 0.89 to 0.99). However, the analysis was performed by simply pooling the data from 33 diverse studies, which is an inappropriate method for combining studies. We re-analysed the data, stratifying by study, and found that an intact foreskin was associated with an increased risk of HIV infection: combined odds ratio 1.43 (1.32 to 1.54) with a fixed effect model and 1.67 (1.25 to 2.24) with a random effect model. There was significant between-study heterogeneity (P<0.0001) which was partly explained by stronger associations in studies in high-risk groups. The results from this re-analysis thus support the contention that male circumcision may offer protection against HIV infection, particularly in high-risk groups where genital ulcers and other STDs 'drive' the HIV epidemic. A systematic review is required to clarify this issue. Such a review should be based on an extensive search for relevant studies, published and unpublished, and should include a careful assessment of the design and methodological quality of studies. Much emphasis should be given to the exploration of possible sources of heterogeneity. In view of the continued high prevalence and incidence of HIV in many countries in sub-Saharan Africa, the question of whether circumcision could contribute to prevent infections is of great importance, and a sound systematic review of the available evidence should be performed without delay.
To describe the types of report that are cited by protocols and reviews included in the Cochrane Database of Systematic Reviews.
The citation for each reference included in the Cochrane protocols and reviews published in the Cochrane Database of Systematic Reviews in issue 1, 1999 of The Cochrane Library were categorized by reference type (e.g., journal article, conference proceeding, book chapter, personal communication, Cochrane review).
Of a total of 24,913 citations, 21,694 (87.1%) were references to journal articles. There was a significant difference between the proportion of references to studies that were journal articles (12,348 of 13,472; 91.7%) and the proportion of other references in this category (9,346 of 11,441; 81.7%).
The great majority of studies included in Cochrane reviews at the beginning of 1999 had been published as journal articles.