While there has been some increasing interest in external validity, most work to this point has been in assessing the similarity of a randomized trial sample and a population of interest (e.g., Stuart et al., 2010; Tipton, 2011). The goal of this research is to calculate empirical estimates of the external validity bias in educational intervention…

This report summarizes the complex research literature on quantitative methods for assessing how impacts of educational interventions on instructional practices and student learning differ across students, educators, and schools. It also provides technical guidance about the use and interpretation of these methods. The research topics addressed…