*6 *

*One percent of the population suffers from a certain disease. There is a blood test for this disease, and it is 99% accurate, in other words, the probability that it gives the correct answer is 0.99, regardless of whether the person is sick or healthy. A person takes the blood test, and the result says that she has the disease. What is the probability that she actually has the disease?*

*(A) 0.99%*

*(B) 25%*

*(C) 50%*

*(D) 75%*

*(E) 98%*

I thought it would just be 0.1*0.99 = 0.0099 but it appears that this is not the case.