I wrote a rather long post on base rates over at the main blog, and I included this graphic. It’s based on this story about a Kansas couple whose was raided by a SWAT team after shopping at a garden store. The police had put them on a suspect list, then swung by their house to test for the presence of drugs in their trash can. Twice the test said there were drugs present, but it turns out that test had up to a 70% false positive rate. I do the math in the other post, but it’s very likely that a positive test only meant a 16% chance of a true positive. Yikes. Anyway, go check out my whole post here.