Potvin C consequences [Two-Stage / GS Designs]

posted by ElMaestro  – Denmark, 2022-06-26 11:11 (611 d 17:15 ago) – Posting: # 23088
Views: 1,793

Hey easy now,

❝ ❝ Of course, ElMaestro is right.

While that sounds good it is only very rarely the truth. :crying:

❝ take a look at some (theoretical) situation: a Sponsor goes with Potvin C (don't ask me why), moreover, he proved that with the current CV and n1 T1E does not exceed 5%.

❝ But as you showed in the lectures and in example above, Potvin C could not ensure 5% for all combinations. Thus, during stage 1 the CV was lower and the resulted T1E was out of 5%.

❝ What would be the right (safe) way out in such situation?

I can't follow you, in particular the parts in red.
Your type I error is not depending on your estimates and thus not depending on whether you went into stage 2 or not. They are depending on the true GMR, the (true) variability, N and the underlying stats assumptions; you may have estimates of the CV and GMR and your N is known.
Note also that when we speak of type I error it is often implied that it is the maximum type I error. By definition, it is on the acceptance borders that you get an idea of the type I errors.

Pass or fail!

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