Multilevel Modeling of Individual and Group Level Mediated Effects

• Published in: Multivariate behavioral research Vol. 36; no. 2; pp. 249 - 277
• Main Authors: Krull, Jennifer L., MacKinnon, David P.
• Format: Journal Article
• Language: English
• Published: United States Lawrence Erlbaum Associates, Inc 01.04.2001
• Subjects: Cluster Analysis; Groups; Individual Differences; Multilevel Analysis; Simulation
• ISSN: 0027-3171; 1532-7906
• DOI: 10.1207/S15327906MBR3602_06

This article combines procedures for single-level mediational analysis with multilevel modeling techniques in order to appropriately test mediational effects in clustered data. A simulation study compared the performance of these multilevel mediational models with that of single-level mediational models in clustered data with individual- or group-level initial independent variables, individual- or group-level mediators, and individual level outcomes. The standard errors of mediated effects from the multilevel solution were generally accurate, while those from the single-level procedure were downwardly biased, often by 20% or more. The multilevel advantage was greatest in those situations involving group-level variables, larger group sizes, and higher intraclass correlations in mediator and outcome variables. Multilevel mediational modeling methods were also applied to data from a preventive intervention designed to reduce intentions to use steroids among players on high school football teams. This example illustrates differences between single-level and multilevel mediational modeling in real-world clustered data and shows how the multilevel technique may lead to more accurate results.