Statistical Power and Optimal Sample Allocation in RCTs Investigating Mediation Effects

• In Event: Experimental Design and Hierarchal Linear Models

Abstract

Mediation analyses in randomized controlled trials (RCTs) can unpack potential causal pathways between interventions and outcomes and help the iterative improvement of interventions. When designing RCTs investigating these mechanisms, two key considerations are (1) the sample size needed to achieve adequate statistical power and (2) the efficient use of resources. The current study has developed closed-form statistical power formulas for RCTs investigating mediation effects with and without covariates under the Sobel and joint significance tests. We have further developed an optimal design framework to identify optimal sample allocations that provide the maximum statistical power under a fixed budget. We have implemented the methods in the R package XXX to improve the accessibility of the work.

Authors

• Zuchao Shen, University of Georgia

• Wei Li, University of Florida

• Walter L. Leite, University of Florida