Fantastic illustration of prior vs. posterior probabilities

People have difficulty internalizing what happens when you have a low error rate in some sort of detector but also have a very low probability event. I ran into this doing social media monitoring when we saw that the majority of items classified as certain uncommon language were wrong.

Check out occurrences of "fuck" in English language books in 1862. Every single result on the front page is a mistake – “suck”, “such”, and “Puck” seem to be the bulk of it.

From a discussion on Carlin's seven dirty words on Hacker News.