Estimation of the standardized mean difference for repeated measures designs

Abstract

This simulation study modified the repeated measures mean difference effect size, dRM=, for scenarios with unequal pre-and post-test score variances. Relative parameter and SE bias were calculated for dRM≠ versus dRM=. Results consistently favored dRM≠ over dRM=with worse positive parameter and negative SE bias identified for dRM=for increasingly heterogeneous variance conditions. © 2009 JMASM, Inc.