Indicators of Evidence for Bioequivalence

Some equivalence tests are based on two one-sided tests, where in many applications the test statistics are approximately normal. We define and find evidence for equivalence in Z-tests and then one-and two-sample binomial tests as well as for t-tests. Multivariate equivalence tests are typically based on statistics with non-central chi-squared or non-central F distributions in which the non-centrality parameter lambda is a measure of heterogeneity of several groups. Classical tests of the null lambda >= lambda(0) versus the equivalence alternative lambda < lambda(0) are available, but simple formulae for power functions are not. In these tests, the equivalence limit lambda(0) is typically chosen by context. We provide extensions of classical variance stabilizing transformations for the non-central chi-squared and F distributions that are easy to implement and which lead to indicators of evidence for equivalence. Approximate power functions are also obtained via simple expressions for the expected evidence in these equivalence tests.