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.