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Isn't it true that using Bayesian inference one should conclude that given a positive DNA match that it is more likely you have a false positive than an actual
by btipling 17y ago
Isn't it true that using Bayesian inference one should conclude that given a positive DNA match that it is more likely you have a false positive than an actual match? That isn't there are greater likelihood that there was a mistake in the DNA testing result than you actually find a match? :/
- gjm11 17y agoIf the person who was tested was chosen at random from the population, then yes. But -- and this is an important point that somehow almost gets omitted when the usual examples of DNA evidence, medical tests, etc., are brought up -- when you're testing someone's DNA against samples from a crime scene, or testing whether a person has a rare disease, it's almost always because you already have evidence that brings Pr(they did it) or Pr(they have the disease) way above the baseline level. And in that case Pr(they did it | DNA evidence), or Pr(they have the disease | test result), may well be quite large. (Of course that's not true if the person with matching DNA was found by some kind of search of a Vast DNA Database, or if the positive result on the medical test was the result of a mass screening exercise that tests everybody.)