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Or, if the false positives are probabilistically independent, just run the same test again. If your test gives back 1% false positives, running it twice gets y
by valleyer 11y ago
Or, if the false positives are probabilistically independent, just run the same test again. If your test gives back 1% false positives, running it twice gets you down to .01%, three times gives you one in a million.
- jessriedel 11y agoUnfortunately, this is essentially never the case. The reason is that if the outcomes were probabilistically independent, then you would just declare a standard protocol of always running the test N times, and call that the test. It's safe to assume that such trivial optimizations have already been done for medical tests.
- valleyer 11y agoFair enough. What is an example of a test that has false positives that are not independent (and why)? Curious now.
- jessriedel 11y agoThe common syphilis test looks for antibodies that are produced in response to the bacteria. However, the body may produce those antibodies (on a continuing basis) for other reasons. If you find these antibodies the first time in a given person, you'll keep finding them when you re-test.