Model Definition - Stepwise Tab

Select the Stepwise tab of the Model Definition dialog to access options to specify the type of regression and certain parameters for stepwise regression.

Method

On the drop-down list, choose the type of regression analysis.

All Effects

Select All Effects to enter all variables into the regression equation in one single block or step.

Forward stepwise

Select Forward stepwise to individually add or delete the independent variables from the model at each step of the regression (depending on your choice of F to enter or F to remove values) until the "best" regression model is obtained.

Backward stepwise

Select Backward stepwise to remove the independent variables from the regression equation one at a time (depending on your choice of F to enter or F to remove values) until the "best" regression model is obtained.

F to enter. Specify the F to enter value in this field. The F to enter value determines how significant the contribution of a variable in the regression equation has to be in order for it to be added to the equation. This option is only available if Forward stepwise or Backward stepwise regression is selected in the Method box.

F to remove

Specify the F to remove value in this field. The F to remove value  determines how "insignificant" the contribution of a variable in the regression equation has to be in order for it to be removed from the equation. This option is only available if Forward stepwise or Backward stepwise regression is selected in the Method box.

If it is desirable in forward stepwise regression to force all (or almost all) variables into the equation (one at a time), then the F to enter value should be set to its minimum (0.0001), and the F to remove value should be set to its minimum (0.0; the F to remove must always be less than the F to enter).

If it is desired in backward stepwise regression, to remove all variables from the equation (one at a time), then the F to enter value should be set to a very large value (e.g., 999) and the F to remove value should be set to a value of similar magnitude (e.g., 998; remember that the F to remove value must always be less than the F to enter value).

Number of steps

The Number of steps field allows you to select the maximum number of steps that STATISTICA will perform before displaying the final results of the stepwise regression analysis. This option is only available if Forward stepwise or Backward stepwise regression was selected in the Method box.

Display results

This Display results box affects the display of results from stepwise (forward or backward) multiple regression analyses. You can elect to review only the final (summary) results of the stepwise regression analysis (select Summary only) or you may review the results after each step of the analysis (select At each step).