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AI & Machine Learning · Foundational

Overfitting

When a model learns training data too closely, including noise, and performs poorly on new data.

Definition

An overfit model has low training error but high validation or test error, which indicates high variance. Causes include too complex a model, too little data or training too long. Remedies include more data, regularization, dropout, early stopping, simpler models, data augmentation and cross-validation.

Example

A decision tree that achieves 100% training accuracy but 70% test accuracy.

Exam tip

Training accuracy high plus validation accuracy low equals overfitting; fix with regularization or more data.

Don't confuse it with

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