A decision tree is a tree-like model used to make decisions based on feature values. It is a popular classification algorithm that is simple to understand and interpret.
Here is an example of how a decision tree works:
Suppose we have a dataset of customers, and we want to predict whether they will churn or not (i.e., leave the company). The dataset includes the following features: age, income, number of family members, and whether the customer has a mortgage.
To build a decision tree, we start at the root node and choose the feature that best splits the data into the churn and non-churn customers. For example, we might find that age is the most important predictor of churn, so we make age the root node.
Next, we split the data into two branches based on the possible values of the age. For example, we might split the data into customers who are under 30 and customers who are 30 or older.
We then repeat this process for each branch, choosing the feature that best splits the data into the churn and non-churn customers. For example, we might find that income is the most important predictor for customers under 30, and the number of family members is the most important predictor for customers 30 or older.
This process continues until we reach a leaf node, which represents the predicted class. For example, a leaf node might represent the prediction that a customer will churn or not churn.
Here is a graphical representation of the decision tree:
In this example, the decision tree is used to predict whether a customer will churn based on their age, income, and number of family members. The tree makes a prediction by starting at the root node (age) and following the branches until it reaches a leaf node, which represents the predicted class (churn or not churn).
Decision trees are simple to understand and interpret but can be prone to overfitting, especially if the tree is allowed to grow too deep. To prevent overfitting, we can prune the tree by removing branches that do not improve the accuracy of the model.