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Why We Need Unseen Data

Why We Need Unseen Data

Imagine preparing for an exam.

If you memorize only the practice questions, you may perform well on those exact questions but struggle when the actual exam contains new questions.

Machine learning behaves similarly.

A model that only memorizes training data may fail when presented with unseen observations.

Using a separate testing dataset helps determine whether the model has truly learned useful patterns rather than simply memorizing examples.

This ability is known as generalization.