title: A simple formula for sample size calculation in equivalence studies.
abstract: Bioequivalence and clinical equivalence can be claimed based on the two one-sided test approach or the confidence interval approach. Consequently the power function of the equivalence test can be derived from either noncentral t-distribution or central t-distribution. The sample size is then determined from the power function either by numerical method or closed formulas. In this paper, we propose a simple formula for sample size calculation based on central t-distribution. The proposed formula has better properties than those currently available and it can be easily applied in all equivalence studies.
authors.affiliation: Pfizer Consumer Healthcare, Morris Plains, New Jersey 07950, USA. paul.zhang@pfizer.com
authors.forename: Paul
authors.initials: P
authors.lastname: Zhang
mesh_terms: D016001:Confidence Intervals; D004341:Drug Evaluation / Q000706:statistics & numerical data*; D008432:Mathematical Computing; D015233:Models, Statistical; D018401:Sample Size; D013810:Therapeutic Equivalency