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. Which of the following hypotheses will determine if the two safes take, on average, the same amount of time to crack?

A) H₀: µ_D ≤ 0, H_A: µ_D > 0
B) H₀: µ_D ≥ 0, H_A: µ_D < 0
C) H₀: µ_D ≠ 0, H_A: µ_D = 0
D) H₀: µ_D = 0, H_A: µ_D ≠ 0