A recent study on heart attack prevention strategies reached the opposite of the expected conclusion. Dalrymple comments on the danger of assumptions in medical testing at Pajamas Media:
There are few phrases more dangerous in medicine than “It stands to reason,” because what stands to reason may in fact not be a good idea, however brilliant it may once have seemed. This is because reality is always more complex than our theories about it; grey is theory, said Goethe, but green i[s] the tree of life.
Perhaps the greatest single intellectual advance in the medicine of the last century was the realization that “it stands to reason” is no reason at all; everything must be studied in the light of experience. There was a good example of this necessity in a recent edition of the New England Journal of Medicine, which studied the effect of giving patients doses of aspirin or clonidine before and after undergoing non-cardiac surgery.