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Isn't the false positive rate the percentage of positives that should have been negative? E.g. if I test 10000 people and 100 of them test positive, but really
by DangitBobby 7y ago
Isn't the false positive rate the percentage of positives that should have been negative? E.g. if I test 10000 people and 100 of them test positive, but really only 50 of those are sick (and almost none of the other 9900 people are), then I have a false positive rate of 50% and a very useful test. Obviously, this is very different from flipping a coin. And flipping a coin could also have a very high false negative rate.
- usrusr 7y agoIt's the rate of actual negatives that are perceived as positives. I make that mistake myself all the time, What helps me avoid it is this: you want a number that is a property of the test method alone, independent of case distributions. A ratio between misidentified positives and identified positives (or true positives) would depend on sample distribution.
- monktastic1 7y agoThe metric you're talking about is called the "false discovery rate": https://en.wikipedia.org/wiki/False_discovery_rate https://en.wikipedia.org/wiki/False_discovery_rate I also have a hard time keeping these all straight: https://en.wikipedia.org/wiki/Sensitivity_and_specificity#Application_to_screening_study https://en.wikipedia.org/wiki/Sensitivity_and_specificity#Ap...