Pregnancy Test Results

Question

Positive Test Result
(Pregnancy is indicated)
Negative Test Result
(Pregnancy is not indicated)
Subject is pregnant
80
5
Subject is not pregnant
3
11

a) Based on the results in the table, what is the probability of a women being pregnant if the test
indicates a negative result? If you are a physician and you have a patient who tested negative
what advice would you give?
b) Based on the results in the table, what is the probability of a false positive? That is, what is the
probability of getting a positive result if the woman is not actually pregnant? If you are a
physician, and you have a patient who tested positive, what advice would you give?
c) Find the values of each of the following, and explain the difference between the two events.
Describe the concept confusion of the inverse in this context.
i. P(pregnant | positive test result)
ii. P(positive test result | pregnant)