When lotteries are infeasible, researchers must rely on observational methods to estimate charter effectiveness at raising student test scores. Considerable attention has been paid to observational studies by the Stanford Center for Research on Education Outcomes (CREDO), which have analyzed charter performance in 27 states. However, the…

Although experiments are viewed as the gold standard for evaluation, some of their benefits may be lost when, as is common, outcomes are not defined for some sample members. In evaluations of marriage interventions, for example, a key outcome--relationship quality--is undefined when a couple splits up. This article shows how treatment-control…