Question

Liar, liar! Sometimes police use a lie detector test to help determine whether a suspect is

telling the truth. A lie detector test isn’t foolproof—sometimes it suggests that a person is

lying when he or she is actually telling the truth (a “false positive”). Other times, the test

says that the suspect is being truthful when he or she is actually lying (a “false negative”).

For one brand of lie detector, the probability of a false positive is 0.08.

a. Explain what this probability means.

b. Which is a more serious error in this case: a false positive or a false negative? Justify

your answer.

Short answer

a) The probability of the mammogram's false-negative rate must be interpreted.

b) We predict that around of people who take a$8\%(or0.08)$ polygraph.

Step-by-step solution

Part (a) Step 1: Given information

We have to tell what this probability means.

Part (a) Step 2: Explanation

• The probability of the mammogram's false-negative rate must be interpreted.
• The test says that the suspect is being truthful

Part (b) Step 1: Given information

We have to tell which is a more serious error in this case

Part (b) Step 2: Explanation

• We predict that around $8\%(or0.08)$of people who take a polygraph.

• The truth will have the polygraph show that they lie.