Question

On discovering that her family had a 70% risk of heart attack, Erin took a treadmill test to check her own potential of having a heart attack. The doctors told her that the reliability of the stress test is 67%. What is the probability that Erin will have a heart attack and the test predicts it?

Answer 1

Let event A represent the heart attack, and event B represent the test being reliable. By the information given, we know that P(A) = 0.7 and P(B) = 0.67. The probability that both are true is P(A∩B).

We must assume that the two events are independent. You can find P(A∩B) by applying the multiplication rule for probabilities:

P(A∩B) = P(A)P(B)

Plug and chug