Data Analysis with Microsoft Excel: Updated for Office 2007

478 Statistical Methods

From the rescaled plot, you would conclude that exponential smoothing

has done a good job of modeling the sales data and that the resulting fore-

casts appear reasonable.

The fi nal part of the exponential smoothing output is the fi nal estimate of

the seasonal indexes, shown in Figure 11-34.

Figure 11-34

Seasonal

indices

The values for the seasonal indexes are very similar to those you calcu-

lated using the seasonal adjustment command. The difference is due to the

fact that these seasonal indexes are calculated using a smoothed average,

whereas the earlier indexes were calculated using an unweighted average.

You’re fi nished with the workbook. You can close it now, saving your

changes.

Figure 11-33

Plot of

forecasted

and observed

sales for the

current and

upcoming year