Answered>Order 71

I got these questions wrong and I was certain I knew the answer… Please help me understand where I went wrong.

1) Suppose that 1% of all people have a particular disease. A test for the disease is 99% accurate. This means that a person who has the disease has a 99% chance of testing positive for the disease, while a person who doesn’t have the disease has a 99% chance of testing negative for the disease.

If a person tests positive for the disease, what is the chance (rounded to the nearest hundredth) that he or she actually has the disease?

0.99