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Advancing the Formulation and Testing of Multilevel Mediation and Moderated Mediation Models

Rockwood, Nicholas John
http://rave.ohiolink.edu/etdc/view?acc_num=osu1489578419777238

Abstract Details

2017, Master of Arts, Ohio State University, Psychology.
Researchers in the social sciences are often interested in explaining causal processes in which the effect of one variable is transmitted to another through one or more intervening (or mediator) variables. Statistical mediation analysis can be used by researchers to gain a better understanding of these causal processes. The methods traditionally used to quantify and test a mediation process, or indirect effect, are not directly applicable when the data are nested hierarchically, which is common in educational, organizational, and behavioral sciences where students may be nested within classrooms, employees may be nested within companies, or repeated measurements may be nested within individuals. Multilevel modeling (MLM) is a method for analyzing hierarchical data that allows for the simultaneous estimation of the effects of variables at multiple levels of the hierarchy. As such, several researchers have proposed methods for testing mediation using MLM. A majority of these methods have focused on models in which the independent variable is a level-2 variable, the mediator is either a level-2 or a level-1 variable, and the dependent variable is a level-1 variable. Although some (Kenny, Korchmaros, & Bolger, 2003; Bauer, Preacher, & Gil, 2006) have focused on models in which all three variables are measured at the lowest level, the methods proposed are not without their shortcomings. The aim of this thesis is to address and mitigate some of these shortcomings, as well as provide advancements in the formulation and testing of a number of interesting effects that can be modeled using MLM. The major contributions include demonstrating how to simultaneously estimate between-group and within-group indirect effects using traditional MLM software. A test for the difference between within-group and between-group indirect effects is also conceptualized and explained. Further, the model is expanded to include multiple mediators with either fixed or random slopes. In the case where one or more paths for one indirect effect covary with one or more paths from another, the covariance between the random indirect effects is derived. Finally, the index of moderated mediation (Hayes, 2015) is applied to the multilevel context to test the moderating effect of a level-2 variable on the within-group and/or between-group indirect effect. To demonstrate the methods discussed throughout this thesis, two real-world datasets are analyzed using MLmed, a free SPSS macro developed in conjunction with this thesis and designed specifically to fit multilevel mediation and moderated mediation models. The parameter estimates obtained using MLmed are comparable to those obtained using Mplus (Muthen & Muthen, 2015) and the lme4 package (Bates, Machler, Bolker, & Walker, 2015) in R (R Core Team, 2016), but with considerably less programming effort required.
Andrew Hayes (Advisor)
Paul De Boeck (Committee Member)
Duane Wegener (Committee Member)
176 p.
Educational Psychology; Psychology; Quantitative Psychology
multilevel modeling; mediation; multilevel mediation; moderated mediation; conditional process analysis; mixed effects models; SPSS

Recommended Citations

Citations

  • Rockwood, N. J. (2017). Advancing the Formulation and Testing of Multilevel Mediation and Moderated Mediation Models [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1489578419777238

    APA Style (7th edition)

  • Rockwood, Nicholas. Advancing the Formulation and Testing of Multilevel Mediation and Moderated Mediation Models. 2017. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1489578419777238.

    MLA Style (8th edition)

  • Rockwood, Nicholas. "Advancing the Formulation and Testing of Multilevel Mediation and Moderated Mediation Models." Master's thesis, Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1489578419777238

    Chicago Manual of Style (17th edition)

osu1489578419777238
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This open access ETD is published by The Ohio State University and OhioLINK.