Sample size determination in epidemiologic studies.

Sample size determination is an important issue in epidemiologic studies. Standard methods for determining sample size in cohort and case-control studies have generally been restricted to dichotomous disease and exposure variables and discrete confounding variables, and are based on simplifying assumptions that could often be unrealistic. Methods for sample size determination that make less restrictive and more realistic assumptions regarding the distribution of disease, exposure and confounding variables and which more closely parallel the analyses that are performed on the data, after the study has been conducted, have been developed in recent years. In this article some recent developments in the methodology for sample size determination in epidemiologic studies are reviewed.