A Bank Is Trying to Determine Which Model of Safe

question 101

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. Assuming the difference D is normally distributed, which of the following is the 95% confidence interval for μ_D?

• A) [-1.7537, 5.7537]
• B) [-1.1459, 5.1459]
• C) [-0.6739, 4.6739]
• D) [-0.5368, 4.5368]

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