A Bank Is Trying to Determine Which Model of Safe

question 44

Multiple Choice

A bank is trying to determine which model of safe to install. The bank manager believes that each model is equally resistant to safe crackers but sets up a test to be sure. He hires nine safe experts to break into each of the models, timing each endeavor. The results (in seconds) are given next, paired by expert. Let D be the difference: Time to break Safe 1 minus Time to break Safe 2. Should we conclude that the average time it takes experts to crack the safes does not differ by model at the 5% significance level?

• A) Yes, the 95% confidence interval for μ_D contains 0.
• B) No, the 95% confidence interval for μ_D does not contain 0.
• C) No, the 95% confidence interval for μ_D contains 0, but the absolute value of the upper bound is larger than the absolute value of the lower bound.
• D) There is not enough information to determine the answer.

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