3 ms·

A coin flip won’t be nearly 50% accurate.

• lostlogin 6y ago
  ELI5 - If the test has 50% accuracy and is producing equal false positives and false negatives, is the coin producing inferior results?
  • ls612 6y ago
    No because Pr(Infected) << Pr(Not Infected) even in the places with the most spread right now.
  • dap 6y ago
    Suppose you test a population of 100 people in which 10 are infected. The coin flip test reports 50 people infected on average. Among those positive tests, at least 40 have to be to be false positives Because there are only 10 infected to begin with. That’s a false positive rate at least 80%. Among negatives, we would expect 5 to be false (since 10 people are infected and each of them have a coin flip chance of testing negative) or 10%. I’m not sure that you can have a test that’s 50% accurate and errs equally in both directions. At least, I’m not sure what it would mean.