From The Economist:
Signs of the times
Feb 22nd 2007 | SAN FRANCISCO
From The Economist print edition
Why so much medical research is rot
PEOPLE born under the astrological sign of Leo are 15% more likely to be admitted to hospital with gastric bleeding than those born under the other 11 signs. Sagittarians are 38% more likely than others to land up there because of a broken arm. Those are the conclusions that many medical researchers would be forced to make from a set of data presented to the American Association for the Advancement of Science by Peter Austin of the Institute for Clinical Evaluative Sciences in Toronto. At least, they would be forced to draw them if they applied the lax statistical methods of their own work to the records of hospital admissions in Ontario, Canada, used by Dr Austin.
How likely is a certain disease to be found above chance, given a certain condition? The basic logic is that, if you test 20 hypothesis individually, with a 5% threshold, one in 20 will, of course, be found to be "above chance". So there you have it: a huge load of hoax reports, duly stamped out in the best medicine journals, with sheer superstitious evidence. Dr Peter Austin really deserves merit for what he did.
Journalists will be sad to know about this one. Less chance for that nice front-page report:
"Doctors reporting increased risk of severe cancer for feeding the monkeys at the zoo."