9.4.1 - Early stopping

• Early stopping explicitly restricts the growth of the tree.

• There are several ways we can restrict tree growth but two of the most common approaches are to restrict the tree depth to a certain level or to restrict the minimum number of observations allowed in any terminal node.

• When limiting tree depth we stop splitting after a certain depth (e.g., only grow a tree that has a depth of 5 levels).

• When restricting minimum terminal node size (e.g., leaf nodes must contain at least 10 observations for predictions) we are deciding to not split intermediate nodes which contain too few data points.