[teruakohatu]

> if you get a positive for a horrid cancer with a 90 percent false positives you should be afraid.

No you should not panic, anymore than you should celebrate and buy a yatch if you think you have 10% chance of winning a lottery.

The doctor should phrase it as "the test indicates you have a 10% possibility of cancer. The majority of people who test positive do not have cancer. Further testing is required to confirm or rule it out."

Going with the expected value of 10% of a horrid thing is still bad, or 10% of $100m is still $10m, is not applicable to a single non repeated event.

[halpert]

The GP wasn’t saying go out and kill yourself because you are definitely condemned. They were highlighting that you still have an extremely elevated chance of having cancer. If you got into your car and found out you had a 10% chance of being in a fatal accident, would you not worry? Sure, there is a 90% probability you’ll be fine, but the probability for most other people is 99.999%. Pretending like there isn’t a potential issue is dangerous and willful ignorance.