Weekly Sales of the Weber Dicamatic Food Processor for the Past

Essay

Weekly sales of the Weber Dicamatic food processor for the past ten weeks have been: $$\begin{array} { c r | c r } \text { Week } & \text { Sales } & \text { Week } & \text { Sales } \\1 & 980 & 6 & 990 \\2 & 1040 & 7 & 1030 \\3 & 1120 & 8 & 1260 \\4 & 1050 & 9 & 1240 \\5 & 960 & 10 & 1100\end{array}$$
a. Determine, on the basis of minimizing the mean square error, whether a three-period or four-period simple moving average model gives a better forecast for this problem.
b. For each model, forecast sales for week 11.