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Wednesday, September 07, 2016


First, there is the general issue of using screening tests to identify deviant behavior and then apply action to those identified as deviant, and second, there is the use of this particular study to do it.

There is a whole field in tests & measurements devoted to screening tests. The classic example of the frailty of their use is the test which is 99% sensitive and 99% specific, applied to a population in which the behavior is 1 percent present. Roughly half of the positive test results will be false positives. To apply any treatment or prevention to a group in which half are not appropriate is highly
questionable. Of course, higher prevalence reduces the proportion of false positives, and lower sensitivity and specificity increase it, but the point is made.

Second, there is the use of this particular study to identify the deviant behavior. It is a non-random study with a highly skewed sample. Forget the validity of the test itself, and just look at the sample! Then, consider whether this study alone has enough evidence to allow any claim of validity. Of course it doesn't.

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