A meta-analysis by Tran, Sanchez, Arellano, and Swanson (2011) of the published RTI literature found that the magnitude of effect size (ES) between responders and low responders at posttest was significantly moderated by the pretest ES and the type of dependent measure administered, whereas no significant moderating effects were found in the mixed…

A new effect size representing the predictive power of an independent variable from a multiple regression model is presented. The index, denoted as r[subscript sp], is the semipartial correlation of the predictor with the outcome of interest. This effect size can be computed when multiple predictor variables are included in the regression model…

Calculation of the statistical power of statistical tests is important in planning and interpreting the results of research studies, including meta-analyses. It is particularly important in moderator analyses in meta-analysis, which are often used as sensitivity analyses to rule out moderator effects but also may have low statistical power. This…