In a tree built with PrecisionTree, there are two blue values at each end node, and the top one is a probability. Why are so many of these probabilities 0 in the finished tree in Figure 10.10? What do...

In a tree built with PrecisionTree, there are two blue values at each end node, and the top one is a probability. Why are so many of these probabilities 0 in the finished tree in Figure 10.10? What do the remaining (positive) probabilities represent?