There is a tendency for scales that are very sensitive to change to amplify statistically significant changes that may be clinically irrelevant. Take for example the trial of 2% minoxidil against placebo for androgenetic alopecia in women.14 This study found a statistically significant increase in non-vellus target area hairs in the minoxidil-treated group versus the vehicle-treated group after 32 weeks (P= 0-006): although the "subjects discerned no difference". The study, which was otherwise well conducted, should have concluded something along the lines of, "something seems to be happening, but it is not clinically useful yet". However, the authors' conclusion was that, "Two per cent minoxidil appears to be effective in the treatment of female androgenetic alopecia". Effective for whom?
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