[Show abstract][Hide abstract] ABSTRACT: The goal of this study is to compare the resampling methods including bootstrap and permutation tests against classical methods for paired samples. A simulation study was conducted to see the performance of both parametric and nonparametric methods under various assumptions such as non-normal populations and small or large sample sizes. The results of the simulation study are with respect to type I error and power of the test.
Full-text · Article · Apr 2015 · International Journal of Mathematical Education
[Show abstract][Hide abstract] ABSTRACT: The problem of two-group classification has implications in a number of fields, such as medicine, finance and economics. This study aims to compare the methods of two-group classification. The minimum sum of deviations and linear programming model, linear discriminant analysis, quadratic discriminant analysis, and logistic regression, MANOVA test-based classification and the unpooled T-square test-based classification methods, support vector machines and k-nearest neighbor methods and combined classification method will be compared for data structures having fat-tail and/or skewness. The comparison has been carried out by using a simulation procedure designed for various stable distribution structures and sample sizes.
No preview · Article · Dec 2014 · Communication in Statistics- Simulation and Computation
[Show abstract][Hide abstract] ABSTRACT: Log-linear modelling is advanced as a procedure to identify factors that underlie the relative frequency of occurrence of various characteristics. The purpose of this study is to present a modelling effort using log-linear models to estimate the relationships between driver's fault and carelessness and the traffic variables such as gender, accident severity, and accident time. The study was conducted in four different districts in Ankara, the capital of Turkey. There were 1,325 people selected for the study; and they were asked whether they had been in an accident. Four hundred and forty-eight of them answered that they had been involved in an accident. As drivers, 276 out of 448 people, namely 61.6%, had traffic accidents. The data on the variables, namely gender, driver's fault and carelessness, accident severity and accident time, were collected through a questionnaire survey. Detailed information has been created based on this information. The analysis showed that the best-fit model regarding these variables was the log-linear model. Furthermore, the odds ratio between these variables, the associations of the factors with the accident severity and the contributions of various factors, and the multiple interactions between these variables were assessed. The obtained results provide valuable information in regard to preventing undesired consequences of traffic accidents.
No preview · Article · Dec 2012 · Promet-Traffic & Transportation
[Show abstract][Hide abstract] ABSTRACT: This article presents tests for the interaction in a two way table with one observation per cell. The conventional linear model theory cannot be used to check for the interaction when there is exactly one observation per cell (no replication) in two way ANOVA models. For this purpose, two different approaches are presented in the literature. The first of these approaches is to assume a specific functional form for the interaction terms. The second approach is not to assume a specific functional form for the interaction terms. In this article, we present four additivity tests by proposed Tusell (1990), Boik (1993a), Piepho (1994), Kharrati-Kopaei and Sadooghi-Alvandi (2007) for second approach. We compared their performance by means of simulation studies with respect to the power.
No preview · Article · Jan 2012 · Gazi University Journal of Science
[Show abstract][Hide abstract] ABSTRACT: In this study it was aimed to determine the adherence of Pseudomonas and Candida to contact lens surfaces, and to determine the difference in adherence between five contact lens types. Biofilm-negative control strains were also used to emphasize the difference between biofilm-positive and biofilm-negative strains in adherence.
Five different soft contact lenses were used to investigate the adherence of Pseudomonas aeruginosa and Candida albicans strains. P. aeruginosa ATCC 27853, P. aeruginosa ATCC 10145, C.albicans ATCC 10231 standard strains and C. albicans clinical isolate were included in the study. Slime formation was investigated by two methods; modified Christensen macrotube method, and a modified microtiter plate test. P. aeruginosa and C. albicans slime formation on soft contact lenses was studied in adherence and separation phases. Pseudomonas and Candida suspensions were serially diluted and inoculated to blood agar and sabouraud dextrose agar surfaces respectively. After overnight incubation, the colonies were counted. Sterile unworn contact lenses were used as negative controls, and bacterial and fungal culture suspensions were used as positive controls. The experiments were conducted in three parallel series.
The number of adherent Pseudomonas was as follows from high to low in polymacon, etafilcon A, hilafilcon, ocufilcon and lotrafilcon contact lenses respectively. However, the number of adherent yeast were determined higher in lotrafilcon and ocufilcon contact lenses, followed by hilafilcon, etafilcon A and polymacon contact lenses. Biofilm-negative Pseudomonas ATCC standard strain and Candida clinical isolate were used to confirm that the number of adherent cells were lower than the biofilm-positive ones.
This study demonstrates that in addition to the contact lens properties, the microorganisms themselves and their interactions with the lens material also play an important role in adherence.
No preview · Article · Apr 2011 · Albrecht von Graæes Archiv für Ophthalmologie
[Show abstract][Hide abstract] ABSTRACT: The efficacy of aromatase inhibitors incorporated in the ovarian stimulation protocols of poor-responder patients undergoing intracytoplasmic sperm injection-embryo transfer cycles was investigated. A total of 70 poor-responder patients were randomized into two groups on day 3 of their menstrual cycle. In Group A, an aromatase inhibitor (letrozole, 5 mg/day) was administered along with a fixed dosage (450 IU/day) of recombinant FSH (rFSH), whereas Group B were treated with the same rFSH dosage alone. A flexible regimen of gonadotrophin-releasing hormone antagonist was administered in both groups. The mean total dose of rFSH (2980 +/- 435 IU versus 3850 +/- 580 IU, P < 0.05) and serum concentrations of oestradiol on the day of human chorionic gonadotrophin administration (1870 +/- 159 pg/ml versus 2015 +/- 175 pg/ml, P < 0.05) were significantly lower in Group A compared with Group B, respectively. The rate of cycle cancellation due to poor ovarian response was lower in Group A (8.6%) than in Group B (28.6%), ( P < 0.05). The costs of achieving a clinical pregnancy were US$11560 and US$17584, and the clinical pregnancy rates per embryo transfer were 25.8% and 20%, in groups A and B, respectively. In conclusion, adjunctive letrozole administration seems to restore an IVF cycle by decreasing the rate of cycle cancellation and seems to reduce the cost by reducing the total gonadotrophin dosage.
No preview · Article · Oct 2009 · Reproductive biomedicine online
[Show abstract][Hide abstract] ABSTRACT: The effect of dehydroepiandrosterone (DHEA) supplementation on cycle outcome was assessed in patients with poor ovarian response. In total, 19 poor responder patients who were scheduled to undergo a second intracytoplasmic sperm injection (ICSI)/embryo transfer cycle were enrolled and first ICSI/embryo transfer cycles were taken as the control group. All subjects were given DHEA supplementation (25 mg t.i.d.) for at least 3 months prior to their second ICSI/embryo transfer cycle. In both cycles a fixed dose of rFSH (300 IU/day) and human menopausal gonadotrophin (HMG) (75 or 150 IU/day) along with a flexible gonadotrophin-releasing hormone (GnRH) antagonist protocol were administered. A favourable decrease was noted in mean day 3 serum oestradiol concentrations after DHEA supplementation (75.14 +/- 28.93 versus 43.07 +/- 11.77; P < 0.01). Increased number of >17 mm follicles (3 +/- 0.7 versus 1.9 +/- 1.3; P < 0.05), MII oocytes (4 +/- 1.8 versus 2.1 +/- 1.8; P < 0.05), top quality day 2 (2.2 +/- 0.8 versus 1.3 +/- 1.1; P < 0.05) and day 3 embryos (1.9 +/- 0.8 versus 0.7 +/- 0.6; P < 0.05) were achieved in DHEA-supplemented cycles. Cycle cancellation rates were reduced (5.3% versus 42.1%; P < 0.01), and the pregnancy rate per patient and clinical pregnancy rate per embryo transfer (47.4% versus 10.5%; P < 0.01 and 44.4% versus 0%; P < 0.01) were improved after DHEA supplementation. DHEA supplementation might enhance ovarian response, reduce cycle cancellation rates and increase embryo quality in poor responders.
No preview · Article · Oct 2009 · Reproductive biomedicine online