Post by Tamrin on Mar 30, 2012 21:54:05 GMT 10
Statistics – Tool or Weapon?
The application and misapplication of Bayes’ theorem
[/b][/size]The application and misapplication of Bayes’ theorem
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There is an old saying: "Statistics don't lie… but statisticians sometimes do." This maxim is a corollary of the well known fact that "Garbage In produces Garbage Out" (GIGO). It reaffirms the observation that, no matter how sophisticated any given computer program may be, if you feed it input data that is flawed, the output you will get will also be flawed. Despite this however, most people are usually impressed by complication: the more complicated the computerized algorithm, the more persuasive the results are for anyone who is gullible. The effectiveness of complicated statistics is a case in point.
Bayes‟ theorem (BT) is a statistical principle that is quite enlightening if properly applied. But as with many powerful tools, it can be dangerous if it is misused. BT was specifically developed to answer questions about the validity of tests.
The moral of the story is this: If you are looking for the occurrence of something that is comparatively rare in the general population, your test has to be almost perfectly reliable or you will be fooling yourself if you believe the result you get from using it.
As with the application of any type of logic, a conclusion can only be as reliable as the premises from which it was derived. In other words, as a bare minimum there has to be some relevant evidence.