This tree can then be tested with testing data that has not been used in the model selection or training. Classification and regression trees can be divided to families. More generally, these algoritms can also be called tree-structured methods. Exactly two branches from each nonterminal node. Cross-validation and pruning are used to determine size of tree.
Response variable can be quantitative or nominal.
Predictor variables can be nominal or ordinal, and continuous predictors are supported. Number of branches equals number of categories of predictor. Number of branches varies from two to the number of categories of predictor. AID, MAID, and XAID are for quantitative responses. FIRM comes in two varieties for categorical or continuous response.