Thanks for this. It's surprising how many people have no idea. Because it is so counter-intuitive, it's hard to explain it to people even when you pretty much understand it yourself. You find yourself saying, "Your chances of having a false positive are greater than your chances of having the condition in the case of this test that's supposed to be 99% ‘accurate,’” and you are still confusing yourself by thinking, "wait a minute..."

I'm going to have to commit to memory your lucid comments about sensitivity vs specificity.