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Old 07 February 2014, 09:16 PM
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Richard W Richard W is offline
Join Date: 19 February 2000
Location: High Wycombe, UK
Posts: 26,361

Originally Posted by GenYus234 View Post
In case anyone is wondering, testing 1,000 people would produce 51 positive tests, 50 false positives and 1 true positive. So if you tested positive, there is a 1/51 chance you are the true positive test.
It's not quite that simple since there's a 5% chance it will miss the true positive - I think that's a factor so that the actual answer comes out to exactly 2% though. (I can't be arsed to do the sums now but I've done them before...)
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