feeling uneasy about your first christmas love letter from the onion fields? this might ease your mind: the false positive paradox : DarkNetMarkets | Torhoo darknet markets

I wish I could credit the OP of this small food for thought, but alas when the axe came and cut the first head of the hydra (r/darketmarkets on kekkit), it took everything with him. But, I saved the good part of it. The numbers are outdated, as this post dates back to 2016-2017, but the concept remains.


The false positive paradox is a fascinating phenomena of statistics. You can read about it in detail here.

Here is a short version of it. Let's say you have a rare disease that affects 1 in a million people. There is a test that is 99% accurate. If you are tested positive, what is the probability you have the disease? You might think 99%.But it is actually .01%. That's because a 99% test generates a shit-ton of false positives when the probability of an event is really low.

So what does this mean for darknet shipments? Well, first class mail is about 200M per day. I would guess darknet shipments at about 6,000 per day. (would love a correction if someone knows a better number) That means the probability of a piece of mail having drugs is about .00003.

So let's say the USPS has a drug detector that is 99% accurate and they scan all 200M pieces of mail. That means they will generate (.01)*200,000,000 = 2,000,000 false positives. There is just no way that is every going to fly because they would need secondary investigation on all of those. And 99% would be extremely difficult, if not impossible to achieve. As a point of comparison, the TSA is about 4% on simulated terrorist tests.

In order to get it to where they had a reasonable number of false positives compared to the number of drugs shipped, they would need a test that was about 99.99% accurate, giving .0001*200,000,000 = 20,000 false positives. That's a really, really, really accurate test.