A General Model for Testing Mediation and Moderation Effects

Department of Psychology, University of South Carolina, Barnwell College, 1512 Pendleton St., Columbia, SC 29208, USA.
Prevention Science (Impact Factor: 2.63). 12/2008; 10(2):87-99. DOI: 10.1007/s11121-008-0109-6
Source: PubMed

ABSTRACT This paper describes methods for testing mediation and moderation effects in a dataset, both together and separately. Investigations of this kind are especially valuable in prevention research to obtain information on the process by which a program achieves its effects and whether the program is effective for subgroups of individuals. A general model that simultaneously estimates mediation and moderation effects is presented, and the utility of combining the effects into a single model is described. Possible effects of interest in the model are explained, as are statistical methods to assess these effects. The methods are further illustrated in a hypothetical prevention program example.

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    • "The product of coefficients method for testing statistical mediation was applied using MPlus Version 5.2 (Muthén & Muthén, Los Angeles, LA), with percentile bootstrapping implemented to adjust asymmetric confidence limits and address biased standard errors (Fairchild, Mackinnon, Taborga, & Taylor, 2009; MacKinnon, Lockwood, Hoffman, West, & Sheets, 2002). This method provides a balance of power and Type I error and supports the use of mediation when there may not be strong predictoreoutcome associations , whereas the causal steps and difference in coefficients methods are less advisable for relatively smaller samples, and are more susceptible to Type II errors (Fairchild & MacKinnon, 2009; Fritz & MacKinnon, 2007; MacKinnon et al., 2002). The product of coefficients method involves regression of outcomes on the mediator and predictors, and regression of the mediator on the predictors , yielding two coefficients that link predictors to the mediator and the mediator to the outcome, with the product of these coefficients providing an estimate of the mediated/indirect effect (ab). "
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    • "We also expected that promoting prosocial behavior could result in an improvement of academic achievement in accordance with previous findings highlighting the long-term effect of prosociality on academic achievement (Caprara et al. 2000). Finally, in line with the prevention research and its implications for mental health interventions (Fairchild and Mackinnon 2009), we investigated the presence of moderation effects among participants in responding to CEPIDEA as well as possible mediation mechanisms through which CEPIDEA could have achieved its effects (i.e., the impact of prosocial behaviors on the reduction of aggressive behaviors; see Caprara et al. 2014). Overall, in pursuing the enhancement of prosocial behaviors in the classroom, CEPIDEA paid close attention to its impact on peer relationships using peer ratings to assess the changes in behavior (prosocial behavior and aggression ) due to the intervention condition. "
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    • "*p<.05; **p<.01 J Fam Viol potential presence of indirect effects in the absence of a significant direct effect has been documented (Fairchild and MacKinnon 2009; Shrout and Bolger 2002). Thus, we tested family and peer support as potential mediators in the child abuse-social functioning relation in all cases. "
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    ABSTRACT: This study examined the relationship among child abuse (physical, emotional, and sexual), social support from friends and family, and social functioning in a sample of low income African American children (N=152).With the exception of the association between sexual abuse and peer support, all of the correlations among study variables were significant. The relationship between child physical and emotional abuse and social functioning were mediated by both family and peer support; however, only family (not peer) support was a significant mediator in the sexual abuse-social functioning link. Additionally, there was no difference found in the strength of mediation via family support versus peer support. Results suggest that mental health professionals should inquire about and attempt to increase children’s levels of social support from family and peers when working with abused youth in order to promote healthy psychological and psychosocial outcomes.
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