Bioequivalence and Bioavailability Forum

Ah, got it, thanks Helmut,

❝ (...a bunch of blah blah blah...)

❝ That’s pure reasoning (wetware).

I think you are saying that:

• 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.

That is correct. I don't think it is something I personally can deduce logically by looking at the algo or equations, but it is a correct statement, I believe, based on simulations.
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.