General CHAID Models Quick Specs - Stopping Tab

Select the Stopping tab of the General CHAID Models Quick specs dialog box or the ITREES CHAID Extended Options dialog box to access options to keep a check on the size of the tree. The size of the tree is an important issue in computing the CHAID Trees; you don't want the tree to grow to an undesirable size, which may make the interpretation of results difficult.

Element Name Description
Stopping parameters These parameters determine when the tree building process will terminate.
Minimum n Enter a value for the Minimum n. If the number of observations within the node is less than this value, the node will not be considered for splitting.
Minimum n in child node Use this option to control the smallest permissible number in a child node, for a split to be applied. While the Minimum n parameter determines whether an additional split is considered at any particular node, the Minimum n in child node parameter determines whether a split will be applied, depending on whether any of the resultant child nodes will be smaller (have fewer cases) than n as specified via this option. Note this option is only available on the ITREES CHAID Extended Options dialog box.
Maximum n nodes Enter a value in the Maximum n nodes box to stop splitting on the basis of the number of nodes in the classification tree. Each time a split occurs, the total number of nodes in the tree is examined and the splitting process is stopped if this number exceeds the number specified as Maximum n nodes.
Maximum n levels Use this option to specify the maximum number (n) of levels in the tree. Note this option is only available on the ITREES CHAID Extended Options dialog box.
Prob. for splitting. As described in Basic Tree-Building Algorithm: CHAID and Exhaustive CHAID, the tree building (split selection) will continue until no further splits can be found that are statistically significant (see also Bonferroni adjustment) at the level specified here as the Probability for splitting.
Prob. for merging As described in Basic Tree-Building Algorithm: CHAID and Exhaustive CHAID, the tree building computations involve the merging of predictor categories (artificially created for continuous predictors) that are not statistically significant with respect to the dependent variable (Chi-square tests are computed for categorical dependent variables, and F tests are computed for continuous dependent variables). If no further merging can be performed, giving the Probability for merging defined here, and if no further splits can be performed consistent with the other stopping criteria specified on this tab, then the tree-building (split selection) computations will terminate.