Question

Given the following statistics for women over the age of 50 entering our medical clinic: 1% actually have breast cancer 90% of the women who have breast cancer are going to get a positive test result (affirming that they have the disease) 8% of those that actually don’t have the disease are going to be told that they do have breast cancer (a “false positive”) What’s the actual probability, if a woman gets a positive test result, that she actually does have breast cancer?

Answer 1

Answer: 91.2%

Explanation:

Of the 1% of women that have breast cancer, 90% of those are tested positive with 8% of those being false positive. 8% of 90% is 8.8% so 91.2% chance.