A regional package delivery company is considering changing from full-size vans to minivans. The company sampled minivans from each of three manufacturers. The number sampled represents the number the manufacturer was able to provide for the test. Each minivan was driven for 5,000 miles, and the operating cost per mile was computed. The operating costs, in cents per mile, for the 12 are provided in the data file called Delivery:

a. Perform an analysis of variance on these data. Assume a significance level of 0.05. Do the experimental data provide evidence that the average operating costs per mile for the three types of minivans are different? Use a p -value approach.
b. Referring to part a, based on the sample data and the appropriate test for multiple comparisons, what conclusions should be reached concerning which type of car the delivery company should adopt? Discuss and prepare a report to the company CEO. Use α = 0.05.
c. Provide an estimate of the maximum and minimum difference in average savings per year if the CEO chooses the “best” versus the “worst” minivan using operating costs as a criterion. Assume that minivans are driven 30,000 miles a year. Use a 90% confidence interval.