Similarity testing using paired comparison method

Statistical model and procedure for similarity tests using paired comparison method are developed in the framework of the “two one-sided tests” (TOST) according to the intersection-union test (IUT) principle. Critical values, testing powers and sample sizes for the tests are provided based on the binomial distribution. Confidence intervals used in similarity testing are discussed. Current practice of using the conventional confidence intervals in two-sided similarity testing is criticized. A 100(1 − α)% confidence interval associated exactly with a α-level TOST is provided. Two key points are addressed in the paper. (1) Unlike difference testing, no multiplicity adjustment is needed to achieve an overall α-level in the two-sided similarity hypothesis tests. (2) The conventional two-sided confidence intervals do not match the TOST.