This article develops new closed-form variance expressions for power analyses for commonly used difference-in-differences (DID) and comparative interrupted time series (CITS) panel data estimators. The main contribution is to incorporate variation in treatment timing into the analysis. The power formulas also account for other key design features…

This article examines theoretical and empirical issues related to the statistical power of impact estimates for experimental evaluations of education programs. The author considers designs where random assignment is conducted at the school, classroom, or student level, and employs a unified analytic framework using statistical methods from the…

This paper examines issues related to the statistical power of impact estimates for experimental evaluations of education programs. The focus is on "group-based" experimental designs, because many studies of education programs involve random assignment at the group level (for example, at the school or classroom level) rather than at the student…