This enables you to change the current regression model by adding or removing
terms. The Options settings of the regression menu (or GLM menu) control what
output is produced when the model is updated. After fitting a sequence of
models you can use the Accumulated setting of Further Output to produce a
summary of the various changes you have made. You can also use this menu to
build regression models using a stepwise search.
Terms
Lists the terms in the maximal model (variates or factors, or interactions)
which can be changed in the current model. You can select one or more terms.
Select All
This selects all the terms in the maximal model.
Add
The specified terms are added to the current model. The current model is
updated to contain these terms.
Drop
The specified terms are removed from the current model. They must be present
in the model currently fitted. The current model is updated to reflect terms,
which have been dropped.
Switch
Terms that are present in the model are dropped, and terms that are not
present are added. The current model is updated to reflect the changes.
Try
The effect of changing the model is reported, for each of the terms in turn.
Terms that are present in the model are dropped, and terms that are not
present are added. However, the current model is retained as before.
You can produce a brief summary of potential changes by selecting Display
Changes. You can control whether the previously chosen display options
are printed in the analysis by setting the Display Default Options
checkbox.
Max Number of Steps
Provides a space for you to specify the limit on the number of times to repeat
a stepwise selection, unless no change in the model is made.
Test Criterion
Provides a space for you to specify the criterion for the inclusion and/or
exclusion of terms. The criterion is based on the variance ratios. As the
criteria are ratios of variances, they should not be interpreted as
F-statistics with the usual interpretation of significance.
Forward Selection
Builds a regression model using forward selection. You can specify the terms
to use in the selection process in the Terms List.
Backward Elimination
Builds a regression model using backward elimination. You can specify the
terms to use in the elimination process in the Terms List.
Stepwise Regression
Builds a regression model using stepwise regression. You can specify the terms
to use in the selection process in the Terms List.
Display Changes
If selected, all changes made to the model will be displayed in the output.
Display Monitoring
If selected the progress of the fit of the model will be displayed in the
output.
Display Default Options
If selected, all display options previously selected will be displayed in
the revised analysis.
See Also
ADD, DROP, SWITCH and TRY directives for changing terms in a model.
STEP directive for stepwise search