Here is a fun little puzzle for you, from Scientific American. Curiously appropriate to some of the debates we have been having lately.
Let's say there is a medical test that tests for disease XYZ.
Let's say 1 in 1000 people actually have disease XYZ.
Now this screening test correctly identifies everyone that actually has XYZ. But unfortunately the screening test also has a false positive rate of 5%.
The question is, of the people that are identified by the test as having disease XYZ, what percentage of these people actually have the disease? Put your (approximate) answer in the poll below...