What is Gini Impurity?

Approach: Define the probability of incorrect classification of a random element.

A metric used in decision trees to measure how often a randomly chosen element from a set would be incorrectly labeled. A Gini Impurity of 0 means the node is 'pure' (all elements belong to one class).

Follow-up: Compare it to Entropy.

Key concepts: decision trees, cart, purity.