Department of Economics
University of Maryland
College Park, MD 20740
Institutional Affiliation: University of Maryland
NBER Working Papers and Publications
|November 2019||Assessing External Validity|
with Sebastian Galiani: w26422
In designing any causal study, steps must be taken to address both internal and external threats to its validity. Researchers tend to focus primarily on dealing with threats to internal validity. However, once they have conducted an internally valid analysis, that analysis yields an established set of findings for the specific case in question. As for the future usefulness of that result, however, what matters is its degree of external validity. In this paper we provide a formal, general exploration of the question of external validity and propose a simple and generally applicable method for evaluating the external validity of randomized controlled trials.