High risk of bias: there were treatment differences between groups other than the main intervention. (cochranelibrary-wiley.com)
Significant treatment differences emerged, however, at the 18 - month follow - up time point. (cebc4cw.org)
Variance heterogeneity is a common feature of educational data when treatment differences expressed through means are present, and often reflects a treatment by subject interaction with respect to an outcome variable. (eric.ed.gov)