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This is actually a stats 101 issue. Imagine that most tests only had 5% false positive rate, then if you took 20 tests then chances are at least one of those is
by ig1 13y ago
This is actually a stats 101 issue. Imagine that most tests only had 5% false positive rate, then if you took 20 tests then chances are at least one of those is going to give you a false positive.
- renata 13y agoTo be pedantic on stats 101, the chance of having at least one false positive is actually (1 - (.95^20)) ~= 64%, because it's 1 - the probability of every test not having a false positive.
- niels_olson 13y agoMan, that's not pedantic. That's the critical insight that demonstrates someone is competent to talk about stats at all. I wish more people would take the time to point that out when people make the OP's error.
- ScottBurson 13y agoIn fairness, ig1 just said "chances are...", meaning the odds are better than 50-50.
- rmrfrmrf 13y agoThank you.
- ig1 13y agoYes. But no-one is going to remember "solve x for (1-(.95^x)) > 50" the purpose of the 95% & 20 is that it's easy for people to remember.