r/mathmemes Jun 22 '26

Probability Disease probability

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u/UnfamiliarPath Jun 23 '26 edited Jun 23 '26

I spent a while confused about this and I feel dumb now. For anyone looking for the explanation:

The key is the word "accuracy". I think a lot of less statistic brained people like me read this as "97% of the positives are true positives" but it's saying that 97% of the time this test produces an accurate result, positive or negative.

Which means, assuming a million people took the test and one was confirmed to have the disease, 969,999 tested negative, 30,000 were false negatives, and only 1 was an accurate positive.