The fact that many people here (which I consider smarter and more informed than the average population) misunderstand this, I think proves my point. Mammograms

The fact that many people here (which I consider smarter and more informed than the average population) misunderstand this, I think proves my point. Mammograms under 50 give MORE false positives that real positives. That means it's not even a useful data point. If you have a positive result, it's you're more likely you do NOT have cancer than you do. You really have to understand your base rate of expected occurrence and the effectiveness of the test. These can wildly affect how to interpret the results and tell you if you should even take the test in the first place. Here's a somewhat related Numberphile about false positives: https://www.youtube.com/watch?v=M8xlOm2wPAA https://www.youtube.com/watch?v=M8xlOm2wPAA