Stop estimating post hoc power! [Power / Sample Size]

posted by Helmut Homepage – Vienna, Austria, 2018-05-31 14:45  – Posting: # 18833
Views: 3,536

Hi Valiveti,

» We have conducted a pivotal study for Europe with 48 subjects considering ~80% power, ISCV: 23%.

So you were assuming a GMR of 90%, right?

» The study was bioequivalent and 90% CI is within 80-125 for both Cmax & AUCt.

Congratulations!

» Power of Cmax and AUCt are 92% & 66% respectively.

In this order? Can you give us their CVs and GMRs?

» Kindly guide us how to justify the power less than 80% to HA.

There is absolutely nothing to justify! Post hoc power is irrelevant. I strongly recommend to revise your SOPs covering the statistical / clinical report (i.e., don’t give this stupid value at all).
If a European assessor demands it (extremely unlikely!), ask where post hoc power is required in any of the current guidelines and suggest in a polite way to browse through my lectures (e.g., this pretty old one) or to attend training in basic biostatistics.

There are no routine statistical questions,
only questionable statistical routines.
    David R. Cox

Cheers,
Helmut Schütz
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