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Chapter 5: Q. 4 (page 309)

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

Expert verified

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

b) We predict that around of people who take a8%(or0.08) polygraph.

Step by step solution

01

Part (a) Step 1: Given information

We have to tell what this probability means.

02

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
03

Part (b) Step 1: Given information

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

04

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.

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Most popular questions from this chapter

Dogs and cats In one large city, 40%of all households, own a dog, 32%

own a cat, and 18% own both. Suppose we randomly select a household and learn that the household owns a cat. Find the probability that the household owns a dog.

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a. What probability should replace “?” in the table? Why?

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Suppose we select one of these students at random.

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27

a. People with BMI less than 18.5 are often classed as “underweight.” What percent of

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