Also it was an asthma prevention study, not cognitive functioning one, adding even more "researcher degrees of freedom".
replyDoing such side studies is fine in itself, but selling such shakey results as "This study suggests that high-dose vitamin D3 supplementation during pregnancy may be associated with improved cognitive functioning at age 10 years." is a stretch.
> It's a classic p-hacking trick
replyIt's a hypothesis seeking study. It just invalidated 8 of them and picked 1 ok-ish candidate to run an actual study in.
The only thing wrong here is there's only one format for submitting a paper.
And if the 1 ok-ish candidate study turns out to have significant results, publication bias has to be considered: that dozens or more other studies of vitamin D (or whatever) may have not found significant results of previously ok-ish hypothesis candidates and those negative studies are often not published.
replyI think this is quite the case for vitamin D which has multiple physiologic roles and is studied extensively for relation to many categories of health issues. One more reason why it can be stunningly impressive when something/anything health-related is eventually proven.
Where are you getting "after they corrected for multiple testing the significance of 2 of those disappeared"? The text you quoted says, of the three, one disappeared and two remained.
replyRelevant xkcd
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