system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can wrist-scan age tests determine your age?

I've read that FIFA is able to judge person's age with more than 99% certainty from wrist-scan test. What's the process behind that, how do they determine the exact age?
gpt
Since the auto moderator won't allow an efficient answer here's a slightly longer one.

They can't. Wrist scans are discredited everywhere. You can't tell the difference between a 17 year old and an 18 year old via a wrist scan. You can't even tell a 15 year old or a 19 year old.

You can determine whether the bones have finished growing, but, perhaps unsurprisingly, being 18 or not is only loosely correlated with that actually happening.

We all knew people who were done growing at 14 and people who were still doing it at 19 so this shouldn't be a huge suprise.

There are doctors who will insist they can do this for money, but they are lying, as at FIFA.

FIFA doesn't care though. They care about the appearance of a fair competition so false positives are fine by them.