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Essay

Explain what a performance gap across two data distributions suggests

Question: A classifier performs well on new examples that resemble its training data, but its accuracy drops on a different evaluation set collected from another source. Explain why this can happen and what the gap says about the training data.

Sample answer: This pattern points to a data mismatch problem. The model does well on new examples from the training distribution because it has learned that pattern of data. It performs worse on the evaluation set from the other source because those examples come from a different distribution. The gap suggests that the training set is not a good match for the evaluation data.

Key points:

  • The model generalizes well to new data drawn from the training distribution.
  • The model performs worse on data drawn from a different dev/test distribution.
  • This difference in performance is a sign of data mismatch.
  • The training set does not adequately reflect the dev/test distribution.

Rubric: The answer should state that the model can succeed on data similar to its training examples but fail on the dev/test set because the two distributions differ, and that this indicates the training data is a poor match for the evaluation data.

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Updated 2026-08-12

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