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—I share Dr Haines' concerns about superstitions that can arise from unexamined experience, but there are many useful ways to analyze experience, only one of which is a formal, prospective clinical trial. In fact, one might consider a randomized clinical trial to be a form of "final inspection" of a promising idea that almost always comes from other learning processes. Indeed, most human knowledge comes from sources other than randomized controlled trials.Systematic observation, carefully interpreted, led the Northern New England Cardiovascular Study Group to impressive success and saved lives. By continuing their study and observations together, the surgeons are learning steadily about which specific factors probably contributed to that success and which did not.Perhaps Dr Sheikh is correct that "spontaneous" improvements or "a general trend toward improved outcomes" may explain the gains of the Northern New England group, but I doubt it. First, trended over time, the results
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