Refer to the gasoline sales time series data in the given table.

WeekSales (1000s of gallons)

1 18

2 21

3 19

4 23

5 17

6 16

7 21

8 17

9 22

10 19

11 14

12 22

Compute four-week and five-week moving averages for the time series. If required, round your answers to two decimal places.

5 17

6 16

7 21

8 17

9 22

10 19

11 14

12 22

b. Compute the MSE for the four-week and five-week moving average forecasts. If required, round your intermediate calculations to four decimal places and round your final answers to three decimal places.

MSE for four-week moving average =

MSE for five-week moving average =

c. What appears to be the best number of weeks of past data (three, four, or five) to use in the moving average computation? Recall that MSE for the three-week moving average is 12.027.