Testing superiority and non-inferiority hypotheses in active controlled clinical trials. 
Switching between testing for superiority and non-inferiority has been an important statistical issue in the design and analysis of active controlled clinical trial.  In practice, it is often conducted with a two-stage testing procedure.  It has been assumed that there is no type I error rate adjustment required when either switching to test for non-inferiority once the data fail to support the superiority claim or switching to test for superiority once the null hypothesis of non-inferiority is rejected with a pre-specified non-inferiority margin in a generalized historical control approach.  However, when using a cross-trial comparison approach for non-inferiority testing, controlling the type I error rate sometimes becomes an issue with the conventional two-stage procedure.  We propose to adopt a single-stage simultaneous testing concept as proposed by Ng (2003) to test both non-inferiority and superiority hypotheses simultaneously.  The proposed procedure is based on Fieller's confidence interval procedure as proposed by Hauschke et al. ( 1999).