Conditional probability is quite helpful for discussing disease testing, particularly for cases where false positives and false negatives are possible. For the following scenario, we'll use events A and B as follows:
Let A be the event that a patient has a disease.
Let B be the event that a patient tests positive for the disease.
Assume that we know that about 5% of our population has the disease. Also assume that we know that the probability of a positive test given that the person has the disease is 97%. Finally, assume that the test gives a false positive 4% of the time.
What is the probability of a person having the disease (event A)?
A) 5%
B) 95%
C) 97%
D) 4%
.
What is the probability of a positive test given that the person has the disease (event B | A)?
A) 97%
B) 4%
C) 5%
D) 96%

Choose the correct answer.

What is the probability of a false positive (not having the disease but testing positive) (event B | not A)?

A) 4%
B) 95%
C) 1%
D) 97%