Discussion:
The ELISA test for AIDS was used in the screening of blood donations in the 1990s. As with most medical diagnostic tests, the ELISA test is not infallible. If a person actually carries the AIDS virus, experts estimate that this test gives a positive result 97.7% of the time. If a person does not carry the AIDS virus, ELISA gives a negative result 92.6% of the time. Experts also estimate that 0.5% of the American public carries the AIDS virus.
Q: Suppose that someone tells you that they have tested positive. Given this information, what is the probability that the person actually carries the AIDS virus?