My Favorite Probability Problem by Daniel Jaouen


Let’s say there is a new disease in the population that we are designing a test for. Say that the test is always accurate if you have the disease (no chance of a false negative), but there is a 1% chance that, if you don’t have the disease, the test will turn up positive (a false positive).

What is the probability that you have the disease given the fact that your test came up positive?