  Tang derived the exact power formulae for t tests and analysis of covariance
(ANCOVA) in superiority, noninferiority 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 noninferiority trials.
