Bret:

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 $2.$

Safe $1$ Safe $2$

$103101$

$90,94$

$6458$

$120,112$

$104103$

$9290$

$145140$

$106110$

$76,74$

Which of the following hypotheses will determine if the two safes take on average the same amlunt of time to crack