FO RE CAST ING
Figure 4. IBM SPSS
input worksheet (showing the “Non-Stop”
movie daily box-office
returns).
products from different categories, specifically Minitab, IBM SPSS and NCSS
on the “Non-Stop” movie data. IBM SPSS
falls into the automatic forecasting category; Minitab and NCSS are semiautomatic
products. A caveat: This is not meant to be
a critical review of any product mentioned.
I let IBM SPSS first do the analysis of
the movie data via its automatic mode,
called “Expert Modeler” (i.e., choose the
model and its parameters and get the
forecasts). Figure 4 shows superimposed
screen shots of IBM SPSS’ worksheet,
showing the “Non-Stop” daily domestic
box-office gross and the menu system
to start the automatic forecasting procedure. The program then gave its recommended model, Brown’s method for data
with linear trend, which uses one smoothing constant to estimate the intercept and
slope of the fitted line (as compared to
Holt’s method, which uses two independent smoothing constants) [1]. IBM
SPSS’ accompanying statistics, forecast
plot and additional output are shown in
Figure 5.
Figure 5: IBM SPSS’ results of “automatic”
forecasting of the “Non-Stop” data.
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