A friend of mine just posted a link to this article on an Email list. I thought it so pertinent, that I recommend it here:
http://www.theatlantic.com/magazine/archive/2010/11/lies-damned-lies-and-medical-science/308269/2/
http://www.theatlantic.com/magazine/archive/2010/11/lies-damned-lies-and-medical-science/308269/2/