City Research Online

Abstract

Basic methods to compute required sample sizes are well understood and supported by widely available software. However, researchers often oversimplify their sample size calculations, overlooking relevant features of their experimental design. This paper compiles and systematises existing methods for sample size calculations for continuous and binary outcomes, both with and without covariates, and for both clustered and non‐clustered randomised controlled trials. We present formulae accommodating panel data structures and uneven designs, and provide guidance on optimally allocating sample size between the number of clusters and the number of units per cluster. In addition, we discuss how to adjust calculations for multiple hypothesis testing and how to estimate power in more complex designs using simulation methods.

Publication Type:	Article
Additional Information:	© 2025 The Author(s). Fiscal Studies published by John Wiley & Sons Ltd on behalf of Institute for Fiscal Studies. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Publisher Keywords:	power analysis, sample size calculations, randomised control trials, cluster randomised control trials, covariates, multiple outcomes, simulation
Subjects:	H Social Sciences > HB Economic Theory Q Science > QA Mathematics > QA75 Electronic computers. Computer science
Departments:	School of Policy & Global Affairs School of Policy & Global Affairs > Department of Economics
SWORD Depositor:	Symplectic Administrator

Export

Downloads