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Title page for ETD etd-05182015-161658


Type of Document Master's Thesis
Author Lachowicz, Mark Joseph
Author's Email Address mark.j.lachowicz@vanderbilt.edu
URN etd-05182015-161658
Title A Novel Measure of Effect Size for Mediation Analysis
Degree Master of Science
Department Psychology
Advisory Committee
Advisor Name Title
Kristopher Preacher Committee Chair
James Steiger Committee Member
Sonya Sterba Committee Member
Keywords
  • mediation analysis
  • effect size
Date of Defense 2015-03-16
Availability unrestricted
Abstract
Mediation analysis has become one of the most popular statistical methods in the social sciences. However, currently available effect size measures for mediation have limitations that restrict their usage to special cases. The goal of this research was to develop a general measure of effect size for mediation analysis that was applicable to a wide variety of models while maintaining the properties of a good effect size estimate. It will be shown how modification of a currently existing effect size measure for simple three-variable mediation models results in a novel effect size measure with properties suitable for general applicability. A matrix method will be proposed for obtaining the measure from complex mediation models and its use will be demonstrated for special cases. In addition, a novel method of variance decomposition using the measure will be proposed which allows for unique and shared contributions of sets of predictors and mediators to be examined in complex mediation models. Finally, two simulation studies will be conducted to examine 1) the properties of the statistic across various population models and 2) the finite sampling properties of the statistic in a multiple mediator model.
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