A simple numerical approach towards improving the two one-sided test for average bioequivalence

For testing average bioequivalence, a simple test that improves upon the two-one sided test (TOST) is derived. The new test uses a critical value that is a non-increasing continuous function of the sample standard deviation, and the function is numerically obtained. Simulation results show that the resulting test performs well in terms of type I error probability; in particular, the test avoids the conservatism of the TOST. Consequently, the test provides better power compared to the TOST, especially when the variance becomes large. Numerical results also show that our test results in power that is very similar to the other improved tests available in the literature. An advantage of our improved test is that it is just as easy to carry out as the TOST. An example is used to illustrate the new test.