Sample size determination for matched studies

Introduction: One faced to matched data when the main object for a study is investigation of the effect of a given factor on an outcome, such that the samples are matched on the some factors which are known as confounders. The response can be according to quantitative or qualitative scales. Matched case-control, before-after and crossover studies are used frequently in medicine. The significant tests are required to sufficient samples. In this paper, formulas for determination of sample size in matched studies are introduced by considering the scale of response and extended for matched case-control studies with multiple controls and illustrated using practical examples. Material & Methods: Using statistical techniques, formulas for determination of sample size are introduced according to the scale of response. Results: The practical examples interpreted in order to clarify the formulas and their applications. Conclusion: One can increase the power and the accuracy of the statistical tests for matched studies, using the introduced formulas.