Model Definition - Advanced Tab

Select the Advanced tab of the Model Definition dialog box to access the options described here.

Method

Select the type of discriminant function analysis from this drop-down list.

Standard

Select Standard to enter all variables simultaneously into the model.

Forward stepwise

Select Forward stepwise to move variables into the model in successive steps; at each step the variable with the largest F to enter value will be chosen for inclusion in the model. The stepping will terminate when no other variable has an F to enter value that is greater than that specified in the F to enter field (see below).

Backward stepwise

Select Backward stepwise to move all selected variables into the equation, and then remove variables one by one; at each step, the variable with the smallest F to remove value will be removed from the model. The stepping will terminate when no other variable in the model has an F to remove value smaller than that specified in the F to remove field (see below).

Tolerance

Enter the tolerance value for the analysis.The tolerance value is discussed in the Introductory Overview. In short, the tolerance value of a variable is computed as the 1 - the R-square of that variable with all other variables in the model. Thus, if a variable has a tolerance value that is smaller than the default value of 0.01, then that variable is more than 99% redundant with the other variables already in the model. If STATISTICA detects a variable with a tolerance value smaller than that specified in this option, it will issue an error message. It is not recommended to set this value much smaller than the default value. The inclusion of highly redundant variables in the analysis may later lead to potentially serious round-off errors in the matrix inversion or canonical analysis, due to matrix ill-conditioning.

Stepwise options

The set of Stepwise options is only available if you select Forward stepwise or Backward stepwise from the Method drop-down list.

F to enter/remove

Enter the F to enter/remove value for the analysis in the F to enter/remove field. In general, in stepwise discriminant function analysis, variables will be entered into the model if their respective F to enter value is larger than that specified in this option; variables will be removed from the model if their respective F to remove value is smaller than that specified in this option. Note that the F to enter value must always be larger than the F to remove value. If, in a forward stepwise analysis, you want to enter all variables, set the F to enter value to a very small number (e.g., 0.0001) and the F to remove value to 0.0. If, in a backward stepwise analysis, you want to remove all variables from a model, set the F to enter value to a very large number (e.g., 9999.), and the F to remove value to a marginally smaller value of equal magnitude (e.g., 9998.).

Number of steps

Enter a value in the Number of steps field to determine the maximum number of steps that will be performed. Note that this option takes precedence over the F to enter/remove values, that is, stepping will terminate after the maximum number of steps has been reached, regardless of whether or not additional variables would qualify for inclusion in or exclusion from the model based on their F to enter or F to remove values.

Display of results

Specify the type of results to display in the Display of results field.  If this field is set to Summary only, then STATISTICA will perform all steps of the stepwise analysis, and only display the full results dialog after the last step. However, that dialog will include an option to review the major summary statistics for the stepwise procedure. Specifically, the Stepwise analysis summary option on the Discriminant Function Analysis Results dialog box - Advanced tab will display for each step in the analysis the respective F to enter or remove value, an associated p-value, the number of variables in the model, and the overall Wilks' Lambda with the associated F-value and significance level. If this field is set to At each step, then STATISTICA will display at each step (starting with step 0) the full results dialog box at each step (starting with step 0).