Evaluating Pretest Effects in Pre-Post Studies

This article presents a method to evaluate pretest effects on posttest scores in the absence of an un-pretested control group using published results of pretesting effects due to Willson and Putnam. Confidence intervals around the expected theoretical gain due to pretesting are computed, and observed gains or differential gains are compared with the original reported results. Examples from the "American Educational Research Journal" and the "Journal of Educational Psychology" are presented that illustrate both support for the original interpretation and evidence for reinterpretation of the results as statistically significant or nonsignificant opposite to the original conclusion. Implications for using the results of meta-analyses in substantive research are discussed. (Contains 4 tables and 2 figures.)