Probability to pass multiple studies [Power / Sample Size]

posted by ElMaestro  – Denmark, 2021-02-19 12:57 (75 d 13:35 ago) – Posting: # 22215
Views: 942

Hi Helmut,

» say, we have n studies, each powered at 90%. What is the probability (i.e., power) that all of them pass BE?
» Let’s keep it simple: T/R-ratios and CVs are identical in studies 1…n. Hence, p(1) = … =p(n). If the outcomes of studies are independent, is p(pass all) = Π p(i), e.g., for p(i=1…6) = 0.90 = 0.906 ~ 0.53?
» Or does each study stand on its own and we don’t have to care? :confused:

Yes to 0.53.
The risk is up to you or your client. I think there is no general awareness, but my real worry is the type I error, as I have indicated elsewhere.
"Have to care" really involves the fine print. I think in the absence of further info it is difficult to tell if you should care and/or from which perspective care is necessary.

Related issue, the one that worries me more:
You test one formulation, it fails on the 90% CI, you develop a new formulation, it passes on the 90% CI. What is the type I error? Well, strictly speaking that would be inflated. But noone seems to give a damn.:-D

Pass or fail!

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