This paper reviews the use of multiple trials, defined as multiple sites or multiple arms in a single evaluation and replications, in evaluating social programs. After defining key terms, the paper discusses the rationales for conducting multiple trials, which include increasing sample size to increase statistical power; identifying the most…

This article discusses the nonuse, misuse, and proper use of pilot studies in experimental evaluation research. The authors first show that there is little theoretical, practical, or empirical guidance available to researchers who seek to incorporate pilot studies into experimental evaluation research designs. The authors then discuss how pilot…