Random Forest

On the Model building tab, select the Random forest check box and click the Random forest button to display this dialog box.

Number of trees. Specify here the number of simple regression trees to be computed in successive forest building steps.

Minimum number to stop. One way to control splitting is to allow splitting to continue until all terminal nodes contain no more than a specified minimum number of cases or objects; this minimum number of cases in a terminal node can be specified via this option.

Minimum child node size to stop. Use this option to control the smallest permissible number in a child node, for a split to be applied. While the Minimum number to stop parameter determines whether an additional split is considered at any particular node, the Minimum child node size to stop parameter determines whether a split will be applied, depending on whether any of the two resultant child nodes will be smaller (have fewer cases) than n as specified via this option.

Maximum number of levels. The value entered here will be used for stopping on the basis on the number of levels in a tree. Each time a parent node is split, the total number of levels (depth of the tree as measured from the root node) is examined, and the splitting is stopped if this number exceeds the number specified in the Maximum number of levels box.

Maximum number of nodes. The value entered here will be used for stopping on the basis of the number of nodes in each tree. Each time a parent node is split, the total number of nodes in the tree is examined, and the splitting is stopped if this number exceeds the number specified in Maximum number of nodes box. The default value 3 would cause each consecutive tree to consist of a single split (one root node, two child nodes).

Prior probabilities. This option is only available if you have selected a categorical dependent variable. This option can be used to specify how likely it is, without using any prior knowledge of the values for the predictor variables in the model, that a case or object will fall into one of the classes. Select Estimated from the drop-down list to specify that the likelihood that a case or object will fall into one of the classes is proportional to the dependent variable class sizes. Select Equal from the drop-down list to specify that the likelihood that a case or object will fall into one of the classes is the same for all dependent variable classes.

OK. Click this button to finalize your changes, close this dialog box, and return to the Model building step.

Cancel. Click this button to close this dialog and return to the Model building step without making any changes.