General CHAID Models Quick Specs - Classification Tab
Select the Classification tab of the General CHAID Models Quick specs dialog box to access the options described here. Note that these options are available only if the dependent (criterion) variable in the current analysis is categorical, and if the Categorical response check box is selected on the Quick tab, i.e., if the goal of the current analysis is to correctly classify cases (observations) into the groups specified in the dependent variable. User-specified (unequal) misclassification costs will not affect the tree-building process itself (which at each step is guided by Chi-square tests; see the Introductory Overview); however, unequal misclassification costs will be used to adjust the risk estimates for the final tree.
| Element Name | Description |
|---|---|
| Misclassification costs | Use these options to assign greater importance to the accurate prediction (classification) for some classes as compared to others. For example, in medical research you may want assign greater importance to the accurate classification of malignant tumors as compared to accurate discrimination between different types of benign forms. In that case, you would assign greater costs to the misclassification of malignant tumors, and lower costs to the misclassification of benign tumors. Note also that, as illustrated in this example, the matrix of misclassification costs does not necessarily have to be symmetric, and in fact it rarely is (i.e., it is more costly to misclassify malignant tumors as benign, then the other way around). |
| Equal | If you select Equal, each off-diagonal element of the predicted class (row) by observed class (column) misclassification costs matrix is set equal to 1.0. |
| User specified | Select User specified to display the User-Specified Misclassification Costs dialog box if you want to adjust the risk estimate for the final tree for unequal misclassification costs; note that the actual tree-building procedure is not affected by the choice of user-specified (unequal) misclassification costs (which at each step is guided by Chi-square tests; see the Introductory Overview). This option is available only if you have selected the Categorical response check box and have selected the codes by clicking the Response codes button on the Quick tab. |