Bioequivalence and Bioavailability Forum

Dear Helmut,

I see, thanks. But allow me one more question. From your given example, let's say we plan with the primary/reasonable assumption CV=20% and start with n1=24. The fixed design would require a sample size of 20 (sampleN.TOST(CV=0.2, alpha=0.05, targetpower=0.8)), correct? What do you mean by "total sample sizes 10-20% higher"? In case the CV turns out to be different and we have to go to stage two or compared to the case where we stop after stage 1? In the former, doesn't it depend on the different CV? E.g. CV=30% as you said, then we would require sampleN.TOST(alpha=0.0294, CV=0.3)-24 = 24 additional subjects and hence it's 100% higher (or using the mean total n from Table II: 39.9/24 = 1.6625). In the latter case we would have 20% (24/20 = 1.2) but is it reasonable to talk about "total" here?

Best,
Ben