A Bank Is Trying to Determine Which Model of Safe

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.