FDA just cleared a $20 Covid-19 antibody test

Re:FDA just cleared a $20 Covid-19 antibody test by kragen on Friday March 20, 2020 @06:35PM (#22642385)

It also means that, if that number is correct, 8.23% of not-yet-infected people will test positive. At a time when only 0.01% of people are infected, that means that 8.2301% of people will test positive, and of those people, on average one person† of every 82301 people will have the infection; the other 82300 are all false positives. They'll need to improve that for this to be useful, since at the time 1% of the population is infected, you're already suffering the worst catastrophe in a century.

† (well, precisely 0.979 out of every 82300.979 people, but the difference is not significant in this context)

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Re:FDA just cleared a $20 Covid-19 antibody test by jupp0r on Friday March 20, 2020 @07:07PM (#22642656)

Yeah, that's the Base Rate Fallacy https://en.wikipedia.org/wiki/Base_rate_fallacy.

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Re:FDA just cleared a $20 Covid-19 antibody test by Maxion on Saturday March 21, 2020 @07:19AM (#22645799)

I'm a little confused at your calculations.

With a population size of 1000 and with 0.01% of the population infected (i.e. 1 individual) with this test we'd get 82 false positives and 0.979 true positives.

For every true positive result in your population, you'll have 8 false positive results and 0,021 false negatives.

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Re:FDA just cleared a $20 Covid-19 antibody test by kragen on Saturday March 21, 2020 @03:44PM (#22649333)

0.01% of 1000 is 0.1 people, not 1 people, and 82÷1 is 82 and not 8, but you're right that my calculations weren't correct either. You'd get 82 false positives and 0.1 (or 0.0979) true positives, so for every true positive result, you have 820 false positives, not 82300 as I said.

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