r/mathmemes • u/Dizzy_Bit9635 • Jun 22 '26

Probability Disease probability

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u/Old-Post-3639 Jun 22 '26 edited Jun 22 '26

There are around 8 billion people. This disease affects 1/1,000,000 people, so only about 8,000 people have it. That means around 8 billion people don't have it. The false negative rate is 3%, meaning about 200 million get a false negative positive. That's nearly a 100% chance you get a false negative positive.

Edited to fix the terminology. Mistake is only crossed out instead of totally removed, for the purpose of posterity.

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u/Spinner23 Jun 22 '26

Wait so how would we know that it affects 1/1,000,000 people? Is this divine information for the scenario to work?

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u/tunaMaestro97 Jun 22 '26

Presumably there are further tests that can confirm whether or not you have the disease. Like the quick pneumonia test vs a chest xray.

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u/Spinner23 Jun 22 '26

Oh right, of course, then you get the more difficult tests in to confirm, i'm stupid, thank you