Test for qualitative interaction in equivalence trials when the number of centres is large.

We propose a generalized testing procedure to test for qualitative interaction in equivalence trails when the number of centres is large. The proposed testing procedure allows for an adaptable definition of qualitative interaction that can take into account the total number of centres. A tuning parameter k (k > or = 0) is introduced to quantify qualitative interaction. The testing procedure is proposed for equivalence trials with symmetric or asymmetric margins. In addition to the test procedure, we also provide explicit formulae for the power calculation. The proposed test is relatively easy to implement using any statistical software. Examples for detecting qualitative interaction are given to illustrate the method. Copyright 2004 John Wiley & Sons, Ltd.