ABSTRACT
Internal validity is critical to the defensibility of impact evaluations. In contrast, internal validity pertains only to impact or causal evaluations, and it is key to their credibility because it is defined as the accuracy of the causal claim. causal claims come from the United States. But program evaluation is critical to the study of international development, and evaluations of program impact are at the center of this growing subfield. The point is that an extraneous event, and not the one under study-the new work-study program-could account for the observed change in graduation rates and other output or outcome variables. The cross-section design compares two or more similar units, one with the program and one without the program, at the same time. The focus here is on numerous threats to internal validity. By providing a checklist, evaluators can anticipate these threats, designing their study to either account for or fend off these threats as well as possible.
