Gym Outfitters sells and services exercise equipment such as treadmills, ellipticals, and stair climbers to gymnasiums and recreational centers. The company’s management would like to determine if there is a relationship between the number of minutes required to complete a routine service call and the number of machines serviced. A random sample of 12 records revealed the following information concerning the number of machines serviced and the time (in minutes)

to complete the routine service call:

Number of Machines Service Time (minutes)
11 115 8 60 9 80 10 90 7 55 6 65 8 70 4 33 10 95 5 50 5 40 12 110

a. Estimate the least squares regression equation.

b. If a gymnasium had six machines, how many minutes should Gym Outfitters expect a routine service call to require?

c. Provide a 90% confidence interval for the average amount of time required to complete a routine service call when the number of machines being serviced is nine.

d. Provide a 90% prediction interval for the time required to complete a particular routine service call for a gymnasium that has seven machines.