Notes on Exact Power Calculations for <i>t</i> Tests and Analysis of Covariance

Tang derived the exact power formulas for t tests and analysis of covariance (ANCOVA) in superiority, noninferiority (NI), and equivalence trials. The power calculation in equivalence trials can be simplified by using Owen’s Q function, which is available in standard statistical software. We extend the exact power determination method for ANCOVA to unstratified and stratified multi-arm randomized trials. The method is applied to the design of multi-arm trials and gold standard NI trials. Supplementary materials for this article are available online.