The manager of a new automobile repair shop wants to establish guidelines for the time it should take to do winter servicing on vehicles. In particular, he is interested in the difference in time between domestic and imported vehicles. He collected data on the number of minutes it took to perform the winter maintenance on 30 randomly selected domestic vehicles and on 30 randomly selected imported vehicles. The data are shown below.

a. Determine the point estimates for the mean amount of time it takes to complete the winter maintenance on the two types of vehicles. Domestic and Imported.

b. Past data indicates the standard deviation for the time it takes to perform winter maintenance on domestic cars is 14.7 minutes. Determine the 95% confidence interval for the meantime it takes the shop to perform winter maintenance on domestic cars.

c. What is a sentence to interpret the confidence interval in part b.

d. Using = 0.05, find an interval estimate for the meantime it takes the shop to perform winter maintenance on imported vehicles.

e. Based on your answers in parts b and d, can it is concluded that, on average, one of the types of vehicles takes longer than the other? Explain and justify the answer.

Domestic 75 58 66 44 78 68 49 78 60 72 80 67 70 77 90 88 93 79 99 94 44 68 78 70 60 79 88 94 66 99

Import 92 89 97 78 90 89 90 88 95 97 99 92 98 80 96 60 61 63 66 59 98 66 97 60 78 88 97 90 89 59