The Growth Limits tab allows you to limit the number of levels in the tree and control the minimum number of cases for parent and child nodes.
Maximum Tree Depth. Controls the maximum number of levels of growth beneath the root node. The Automatic setting limits the tree to three levels beneath the root node for the CHAID and Exhaustive CHAID methods and five levels for the CRT and QUEST methods.
Minimum Number of Cases. Controls the minimum numbers of cases for nodes. Nodes that do not satisfy these criteria will not be split.
- Increasing the minimum values tends to produce trees with fewer nodes.
- Decreasing the minimum values produces trees with more nodes.
For data files with a small number of cases, the default values of 100 cases for parent nodes and 50 cases for child nodes may sometimes result in trees with no nodes below the root node; in this case, lowering the minimum values may produce more useful results.
To Specify Growth Limits
This feature requires the Decision Trees option.
- From the menus choose:
- In the main Decision Tree dialog, click Criteria.
- Click the Growth Limits tab.