We document substantial variation in the effects of a highly-effective literacy pro-gram in northern Uganda. The program increases test scores by 1.40 SDs on average, but standard statistical bounds show that the impact standard deviation exceeds 1.0SD. This implies that the variation in effects...

We provide simple tests for selection on unobserved variables in the Vytlacil-Imbens-Angrist framework for Local Average Treatment Effects (LATEs). Our setup allows researchers not only to test for selection on either or both of the treated and untreated outcomes, but also to assess the...