What is underfitting?

Updated May 17, 2026

Short answer

Underfitting occurs when a model is too simple to capture data patterns.

Deep explanation

It results in poor performance on both training and test data. Increasing model complexity or training time can help.

Real-world example

Using linear regression for image classification.

Common mistakes

  • Stopping training too early.

Follow-up questions

  • How to fix underfitting?
  • Is underfitting always bad?

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