The Process for Establishing Mediation

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Research often seeks to establish the relationship between independent and dependent variables in order to explain human thoughts and behaviours. Understanding how two variables are related provides a description of thoughts and behaviours. However, the fundamental aim of psychology is to postulate and provide empirical evidence for the mechanisms that influence the relationship between variables. Mediation analysis is a useful statistical tool that facilitates a functional understanding of the relationships among variables, rather than merely providing a descriptive account (Preacher, & Hayes, 2004). Mediation refers to the processes that intervene between an independent and dependent variable. For example, within the context of cognitive psychology, attentional processes are thought to mediate the relationship between stimulus (independent variable) and behaviour (dependent variable) (MacKinnon, Lockwood, Hoffman, West, & Sheets, 2002). In the case of mediation, independent and dependent variables are termed predictor and outcome variables, respectively. According to a study conducted by MacKinnon, Lockwood, Hoffman, West and Sheets (2002), 14 methods of analysing mediation effects have been identified that span across disciplines. Of these 14 methods, a causal step method proposed by Baron and Kenny (1986), is the most frequently used method within the field of psychology, and will be the primary focus of this essay. The Sobel test and bootstrapping method have been proposed as alternatives to Baron and Kenny’s (1986) method, and will also be discussed. The process for establishing mediation is as follows; the predictor variable predicts the outcome variable; the predictor variable predicts the mediator; and the mediator predi... ... middle of paper ... ...a mediator of cognitive impairment, negative symptoms, and functioning in schizophrenia. Schizophrenia Bulletin, 35, 798-806. MacKinnon, D. P., Lockwood, C. M., Hoffman, J. M., West, S. G., & Sheets, V. (2002). A comparison of methods to test mediation and other intervening variable effects. Psychological Methods, 7, 83-104. Preacher, K. J., & Hayes, A. F. (2008). Asymptotic and resampling strategies for assessing and comparing indirect effects in multiple mediator models. BehaviorResearch Methods, 40, 879-891. Preacher, K. J., & Hayes, A. F. (2004). SPSS and SAS procedures for estimating indirect effects in simple mediation models. Behavior Research Methods, Instruments, & Computers, 36, 717-731. Shrout, P. E., & Bolger, N. (2002). Mediation in experimental and nonexperimental studies: New procedures and recommendations. Psychological Methods, 7, 422-445.

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