Question 1160758
Look at 10000 people
---------T+--------T- ------Total
D+------9.9-------0.1--------10
D- ----499.5----9490.5  ---9990
Total-- 509.4------9490.6--10000

People who test positive (509.4), 9.9 of them have the disease, 2% probability of having the disease.