Pruning

         Practically, post-pruning overfit trees is more successful because it is not easy to precisely estimate when to stop growing the tree.In this article we will see how to overcome overfitting problem using Post pruning.

We need to follow below steps in order to prune a full grown tree

Here we will see how to calculate Error estimation and Significance test using Chi Square.

Using Error Estimation:

        We need to calculate Error for the child node and we will decide if we need to prune or not based on the error value.

Lets calculate the error for the decision tree we built using Entropy refer the article here.