GIN (Gini Index)

The Gini Index (or Gini Impurity) is a measure used in decision trees to evaluate how well a split separates different groups. Think of it as a score that shows how mixed the categories are within a group; a lower Gini Index indicates a purer group with mostly one category, while a higher score suggests more diversity or mixture. When building a decision tree, the goal is to make splits that result in groups with lower Gini values, improving the accuracy of classifications by creating more homogeneous segments.