Power limbo [Power / Sample Size]

posted by Helmut Homepage – Vienna, Austria, 2021-02-19 13:37 (218 d 18:44 ago) – Posting: # 22216
Views: 1,065

Hi ElMaestro,

» Yes to 0.53.

Shit, expected that.

» The risk is up to you or your client.

Such a case is not uncommon. Say, you have single dose studies (highest strength, fasting/fed), multiple dose studies with two strengths (fasting/fed). Then you get the n = 6 of my example.
If you want a certain overall power, then each study has to be powered to \(p_i=\sqrt[n]{p_\textrm{overall}}\).
With n = 6, for 80% → 96.35% and for 90% → 98.26%. Will an IEC accept that?*

» I think there is no general awareness, but my real worry is the type I error, as I have indicated elsewhere.

I know. ;-)

» 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?

I’m not concerned about a new formulation. The first one went to the waste bin → zero consumer risk. The study supporting the new formulation stands on its own. Hence, TIE ≤0.05.

» Well, strictly speaking that would be inflated. But noone seems to give a damn. :-D

I’m indeed concerned about repeating the study (same formulation) with more subjects. Then you get an inflated TIE.

We have that everywhere. A value in the post-study exam is clinically significant out of range. Follow-up initiated and now all is good. Did the value really improve? There is always inaccuracy involved. Maybe the first one was correct and the second one not.

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