title: Approximate sample sizes for testing hypotheses about the ratio and difference of two means.
abstract: This article deals with a unifying approach to approximate sample size determination for different types of hypotheses formulated in terms of two means of normally distributed data. A simple approximation is given to the sample size required for testing hypotheses about the ratio of the means. The formula includes the situations of testing noninferiority, superiority, or equivalence. We present a more general formula that also covers hypotheses formulated in terms of the difference of means. We show that over a wide range of parameter values the approximation provides reliable sample sizes.
authors.affiliation: Department of Biometry, Dr. Willmar Schwabe Pharmaceuticals, Karlsruhe, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Kieser
authors.forename: D
authors.initials: D
authors.lastname: Hauschke
mesh_terms: D018849:Controlled Clinical Trials as Topic / Q000379:methods*; D003627:Data Interpretation, Statistical; D008432:Mathematical Computing; D016011:Normal Distribution; D013223:Statistics as Topic / Q000379:methods*; D013810:Therapeutic Equivalency