I am not much good at math and have learned much from "Number Watch".
Recently my wife had an x-ray that showed a spot on her lung and the doctor advised her about the probility of Lung Cancer. She went into a panic and was very upset.
Due to "Number Watch", I was able to explain to her that the probability of there actually being a cancer was at worst about 10% and at best less than 1%,not the 99% or 99.9% the doctor led her to believe.
Non-smokers have a 1 in 10,000 chance of getting LC(EPA-1992). If tests were 99% accurate,there would be 100 false positives.She would be 1 out of 101 false positives.Her probability= less than 1%. If test was 99.9% accurate;there would still be 10 false positives and she would have only a 1 in 11,or about 9% chance of being the true positive.
This quieted things down immensely.
Thanks again to John B. and all!!!!