Full ACK [Power / Sample Size]

posted by d_labes  – Berlin, Germany, 2017-12-28 17:41  – Posting: # 18116
Views: 22,097

Dear David,

» In this case, given your simulations above and the expected probability of approximately 12% of the studies having power greater then 95% having in consideration the initial assumptions, post hoc power means nothing.

Full ACK.
But not only in this case, also in other cases. The concept of post-hoc power is flawed by its own.

» But if you had 100 studies instead and 90% of the had >95% power although the sample size was calculated assuming expected power of 80%, some questions and conclusions might be drawn from those results, don't you think? From my understanding of the initial question, this was the case found. So I think that they should start by reviewing how they define their assumptions for the sample size, namely why they assume GMR=1.10 instead of the "normal" 0.95/1.05.

Again: Full ACK.

Regards,

Detlew

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