17. Consider the gasoline purchases for the Spokane Transit Authority given in Table 2. In Example 3, a five-week moving average is used to smooth the data and generate forecasts.

a. Use Minitab to smooth the Spokane Transit Authority data using a four-week moving average. Which moving average length, four weeks or five weeks, appears to represent the data better? Explain.

b. Use Minitab to smooth the Spokane Transit Authority data using simple exponential smoothing. Compare your results with those in part

a. Which procedure, four-week moving average or simple exponential smoothing, do you prefer for these data? Explain.