Idea for paternity

rottingchrist · 2012-08-22T18:18:51+00:00

Make it a routine test among the battery of other tests that are performed on a newborn. And add the cost for it to the hospital bill.

For those who are especially "trusting" of their sweetheart, let them be able to opt out.

rightsbot · 2012-08-22T17:54:17+00:00

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2012-08-23T16:30:43+00:00

Mathematically this may not make sense. I don't have any accuracy numbers in front of me, and if someone could supply them that would be great, but for now I'll just make some up. Let's say paternity testing is right 99% of the time, and currently 50% of all paternity tests reveal paternity fraud. Let's also say that 1% of all pregnancies involve paternity fraud. Finally, half of all paternity fraud is currently caught by a paternity test.

That means that for 20 000 pregnancies there are 200 cases of fraud, 100 of which are tested. There are also 100 tests done on non-fraudulent pregnancies. On average, each of these groups will have one false result. In this case, results are 99% accurate. The tests catch 99 frauds and falsely accuse one non-fraudulent pregnancy (from 100 tested) of fraud. That's only true because fraudulent and non fraudulent pregnancies are being tested at the same rate. Let's see what happens when we test every single pregnancy instead.

20 000 pregnancies, 200 cases of paternity fraud. All 200 fraud cases are tested, the tests say fraud 198 times. Good.

19 800 non fraudulent pregnancies are also tested. 1% of them get false positives for fraud. Bad. We now have 198 frauds stopped and 198 non-frauds accused of paternity fraud. This means that a result indicating paternity fraud would only be right 50% of the time. The two answers to the question of "are you the father" are "almost definitely yes" and "Who knows?"

I didn't expect my numbers to work out this nicely, so I'll keep rolling. Let's pretend that because it's 50/50, people who get a fraud result just flip a coin to decide. Or maybe the doctor doesn't want to admit that the test is next to useless, so s/he flips a coin. Anyway, people 50% of the time believe that a fraud has occurred, and 50% of the time they think the test is wrong. Let's assume that an even number of these are in both groups. 99 frauds and 99 genuines are called frauds, 99 frauds and 99 genuines are called genuine.

Those numbers look familiar. 99 frauds were caught, same as the first example. The only difference is that now 99 genuine pregnancies were also accused of fraud. Meaning that the right number of frauds are discovered, even if half of them are bull.

It won't always work out that way, at least I don't think so, but the point remains: as a test becomes more widespread, its results are less trustworthy, assuming it was initially targeted. Currently paternity tests are much more common in cases where paternity fraud is suspected, and that targeting makes them much more trustworthy. If anyone has these numbers, I'd be happy to run them. Or you can do it yourself, it's not hard.

TL;DR Bayesian probability. 99% accurate doesn't mean 99% accurate.

Title	Idea for paternity
Author	FriarTuck1234
Upvotes	9
Comments	5
Date	August 22, 2012 5:53 PM UTC (13 years ago)
Subreddit	Posted in /r/MensRights
Original Link	https://old.reddit.com/r/MensRights/comments/yncq1/idea_for_paternity/
Archive Link	https://theredarchive.com/r/MensRights/idea-for-paternity.1015262 https://theredarchive.com/post/1015262

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