Stephen Bell

Randomized controlled trials (RCTs) in education are typically conducted in districts and schools that were not selected to represent broader populations of policy interest (e.g., all schools nationwide that could have implemented the education intervention). As a result, findings from these studies may not generalize to these populations. In this project, the research team developed products to help education researchers decide whether to use random or balanced sampling in selecting sites f...

This study was motivated by the observation that most major, multi-site evaluations in education have chosen participating sites (e.g., districts, schools, or grantees) "purposively" and not randomly. This raises possible concerns about the generalizability of the findings from these studies. The goal of this project was to provide evidence regarding the external validity of evaluations that are based on purposive samples.