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> All a power analysis does is reduce the chance that the result is a false negative. It doesn't reduce the chance of a false positive. This is true when we ar
by ramblenode 3y ago
> All a power analysis does is reduce the chance that the result is a false negative. It doesn't reduce the chance of a false positive.
This is true when we are dealing with an uninformative prior, but published research is known to be biased toward positive results and uncorrected multiple comparisons. This situation leads to small sample studies with high random variance being paradoxically correlated with significant results. High random variance appears as a false large effect size in the published result, so if the power is low when calculated with a smaller (adjusted) effect, there is reason to believe that the p-value is inflated. See e.g. Andrew Gelman's work on small sample studies, garden of forking paths or [0].
> Not always. Lots of studies publish as "significant" as soon as they get a p-value just under .05. Inflated effect sizes are certainly a sign that something could be wrong, but it's just one indicator.
Exactly! The implication being the above.
[0] https://en.wikipedia.org/wiki/Why_Most_Published_Research_Findings_Are_False https://en.wikipedia.org/wiki/Why_Most_Published_Research_Fi...