8⁄108 is not the correct calculation. You want 8⁄107. That’s women with cancer and a positive test divided by all women with a positive test. Out of 1000 women, there are 99, not 100 false positives (10% of 990 women without cancer).
or: .01 .8 / (.01 .8 + .99 * .1) = 7.4766355%
8⁄108 is not the correct calculation. You want 8⁄107. That’s women with cancer and a positive test divided by all women with a positive test. Out of 1000 women, there are 99, not 100 false positives (10% of 990 women without cancer).
or: .01 .8 / (.01 .8 + .99 * .1) = 7.4766355%