7.62 ▼ The article on polygraph testing of FBI agents referenced in Exercise 7.51 indicated that the probability of a false-positive (a trustworthy person who nonetheless fails the test) is .15. Let x be the number of trustworthy FBI agents tested until someone fails the test.

a. Describe the probability distribution of x?

b. What is the probability that the first falsepositive will occur when the third person is tested?

c. What is the probability that fewer than four are tested before the first false-positive occurs?

d. What is the probability that more than three agents are tested before the first false-positive occurs?

7.63 Determine the following standard normal (z) curve areas. (Hint: See Examples 7.23 and 7.24.)

a. The area under the z curve to the left of 1.75

b. The area under the z curve to the left of 20.68

c. The area under the z curve to the right of 1.20

d. The area under the z curve to the right of 22.82

e. The area under the z curve between 22.22 and 0.53

f. The area under the z curve between 21 and 1 g. The area under the z curve between 24 and 4