Building the Model

  1. To run a Decision Tree analysis, from the menus choose:

    Analyze > Classify > Tree...

    Figure 1. Decision Tree dialog box
    Decision Tree dialog box
  2. Select Price of primary vehicle as the dependent variable.
  3. Select all the remaining variables as independent variables. (The procedure will automatically exclude any variables that don't make a significant contribution to the final model.)
  4. For the growing method, select CRT.
  5. Click Output.
    Figure 2. Output dialog box, Rules tab
    Output dialog box, Rules tab
  6. Click the Rules tab.
  7. Select (check) Generate classification rules.
  8. For Syntax, select IBM® SPSS® Statistics.
  9. For Type, select Assign values to cases.
  10. Select (check) Export rules to a file and enter a filename and directory location.

    Remember the filename and location or write it down because you'll need it a little later. If you don't include a directory path, you may not know where the file has been saved. You can use the Browse button to navigate to a specific (and valid) directory location.

  11. Click Continue, and then click OK to run the procedure and build the tree model.

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