Guarantors' Mutual, an insurance company, wants to compare the difference in repair costs of moderately damaged cars at two shops. They select a random sample of 12 moderately damaged cars, take each car to both shops, and ask how much the necessary repairs will cost. When they receive the cost estimates for each car, they subtract the cost at the first shop from the cost at the second shop, like this: d=cost at second shopcost at first shop. They create a Q-Q plot of the differences and see that the points in the plot roughly form a straight line.

What is the null hypothesis for this study?

H0:d0 H0:d<0 h0:d>0

What is the alternative hypothesis for this study?

Ha:d0 Ha:d<0 ha:d>0