Description
what is the probability that a person has the disease given that they have received 2 positive test results?
Explanation & Answer
The answer would be 0.99 chances of having the disease. But incase the disease is a very rare one, the answer maybe very surprising. Have a look! "Suppose that you are worried that you might
have a rare disease. You decide to get tested,
and suppose that the testing methods for this
disease are correct 99 percent of the time (in
other words, if you have the disease, it shows
that you do with 99 percent probability, and if
you don't have the disease, it shows that you do
not with 99 percent probability). Suppose this
disease is actually quite rare, occurring randomly
in the general population in only one of every
10,000 people.
If your test results come back positive, what are
your chances that you actually have the disease?
Do you think it is approximately: (a) .99, (b) .90,
(c) .10, or (d) .01?