In the present study, we investigated the relative impact of age- versus schooling-related growth in school readiness skills using four modeling approaches that leverage natural variation in longitudinal data collected within the preschool year. Our goal was to demonstrate the applicability of different analytic techniques that do not rely on…

Applied researchers are increasingly interested in whether and how treatment effects vary in randomized evaluations, especially variation not explained by observed covariates. We propose a model-free approach for testing for the presence of such unexplained variation. To use this randomization-based approach, we must address the fact that the…