Workspace Node: C&RT Regression - Specifications - Advanced Tab
In the C&RT Regression node dialog box, under the Specifications heading, select the Advanced tab to access the following options.
| Element Name | Description |
|---|---|
| Number of surrogates | By choosing "similar" predictors (surrogates) with valid data, cases (observations) with missing data can be classified so that such cases can be included in the analysis. In fact, cases with missing values in the response are treated as "prediction samples" and cases with missing values in the predictor as "surrogate samples." The entry in the
Number of surrogates box controls the number of surrogates that can be chosen by the analysis during the tree-building process. By default, the number of surrogates is 0 (zero), and missing data values are excluded from the analysis.
In general, at every step during the tree building process, Statistica identifies a variable for the next split to improve the accuracy of prediction. If for a particular observation (case) the value for the chosen variable is missing, the program looks to the next-best variable to split on, to act as a "surrogate" for the best variable. If the value for that variable is missing as well, the program looks to the third-best split variable, etc. The Number of surrogates option determines how far down the list of predictors (sorted by the degree of improvement in the accuracy of prediction provided by each respective split candidate) the program will go when attempting to find a surrogate for a variable that has missing data for a particular case. Options / C / W. See Common Options. |
| OK | Click the OK button to accept all the specifications made in the dialog box and to close it. The analysis results will be placed in the Reporting Documents node after running (updating) the project. |