Editing Talk:2476: Base Rate
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Can someone explain here in the comments how, in the explanation, we go from that example of 1% / 5% false-positive rate to a 17% / 83%? [[Special:Contributions/172.69.34.190|172.69.34.190]] 17:14, 16 June 2021 (UTC) | Can someone explain here in the comments how, in the explanation, we go from that example of 1% / 5% false-positive rate to a 17% / 83%? [[Special:Contributions/172.69.34.190|172.69.34.190]] 17:14, 16 June 2021 (UTC) | ||
− | :Take a population of 10,000 tests. From the premise: 1% (100) are true positives and 99% (9,900) are true negatives, regardless of testing. 5% of those TNs (9900*5% = 495) register positive, falsely. We aren't given a false-negative rate, so assuming all 100 TPs register as positive, correctly. | + | :Take a population of 10,000 tests. From the premise: 1% (100) are true positives and 99% (9,900) are true negatives, regardless of testing. 5% of those TNs (9900*5% = 495) register positive, falsely. We aren't given a false-negative rate, so assuming all 100 TPs register as positive, correctly. 595+100=595 people showing as positive, but only the 100 TPs actually truly were, which is slightly ''less'' than 17% (100/595 = 16.8ish%) who have an accurate positive test, leaving a whopping value of slightly more than 83% of tested-positive individuals who were ''wrongly'' identified as positive. [[Special:Contributions/162.158.158.105|162.158.158.105]] 18:11, 16 June 2021 (UTC) |
::Another explanation: the 5% is the answer to "What's the change of having a positive test knowning I'm healthy?" the 83% is the answer to "What's the change of being infected knowing I've got a positive test ?". | ::Another explanation: the 5% is the answer to "What's the change of having a positive test knowning I'm healthy?" the 83% is the answer to "What's the change of being infected knowing I've got a positive test ?". | ||
:::The latter answers "What's the chance of '''not''' being infected, knowing I have a positive test?", as I'm sure you really meant, but that's otherwise an excellent form of summary. [[Special:Contributions/141.101.99.177|141.101.99.177]] 13:33, 17 June 2021 (UTC) | :::The latter answers "What's the chance of '''not''' being infected, knowing I have a positive test?", as I'm sure you really meant, but that's otherwise an excellent form of summary. [[Special:Contributions/141.101.99.177|141.101.99.177]] 13:33, 17 June 2021 (UTC) |