Bioequivalence and Bioavailability Forum

❝ – the alpha₂ that works for n_2,min=2 or 0 or 1 or whatever is not necessarily the alpha₂ that works for n_2,min=1.5*n₁, all other factors being equal.

❝ It is tempting to say power increases with sample size, and since type I error is a kind of power, this is the logic behind the observation.

❝ I think the issue is somewhat more complex than just that. These two-stage thingies are funny objects that defy all kinds of logic.

❝ Does it change anything though??

❝ I mean you and I both argued in the past that universally functional alpha's do not exist, so whenever someone makes a smart/clever/sophisticated/dumb/intelligent/braindead amendment to Potvin B or C etc, then simulations should always be undertaken to make sure the type I error is not compromised.

[…] before using any of the methods […], their operating characteristics should be evaluated for a range of values of n₁, CV and true ratio of means that are of interest, in order to decide if the Type I error rate is controlled, the power is adequate and the potential maximum total sample size is not too great.

• Jones B, Kenward MG. Design and analysis of cross-over trials. Boca Raton: Chapman & Hall/CRC; 2014. p. 365–80.