Back to 3.3 Two Basic Rules of Probability

3.3 Exercise 8

Avg difficulty 2.5

Studies show that about one woman in seven (approximately 14.3%) who live to be 90 will develop breast cancer. Suppose that of those women who develop breast cancer, a test is negative 2% of the time. Also suppose that in the general population of women, the test for breast cancer is negative about 85% of the time. Let B = woman develops breast cancer and let N = tests negative. Suppose one woman is selected at random.

a. What is the probability that the woman develops breast cancer? What is the probability that woman tests negative?

b. Given that the woman has breast cancer, what is the probability that she tests negative?

c. What is the probability that the woman has breast cancer AND tests negative?

d. What is the probability that the woman has breast cancer or tests negative?

e. Are having breast cancer and testing negative independent events?

f. Are having breast cancer and testing negative mutually exclusive?

OpenStax Introductory Statistics 2e, 3.3 Two Basic Rules of Probability, exercise 8

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