Building the Models

  1. Execute the CHAID node that uses all of the predictors in the dataset (the one connected to the Type node). As it runs, notice how long it takes to execute. The results window displays a table.
  2. From the menus, choose Tree > Grow Tree to grow and display the expanded tree.
    Figure 1. Growing the tree in the Tree Builder
    Growing the tree in the Tree Builder
  3. Now do the same for the other CHAID node, which uses only 10 predictors. Again, grow the tree when the Tree Builder opens.

The second model should have executed faster than the first one. Because this dataset is fairly small, the difference in execution times is probably a few seconds; but for larger real-world datasets, the difference may be very noticeable—minutes or even hours. Using feature selection may speed up your processing times dramatically.

The second tree also contains fewer tree nodes than the first. It is easier to comprehend. But before you decide to use it, you need to find out whether it is effective and how it compares to the model that uses all predictors.

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