Essay

Using subset comparisons to test whether more targeted data is needed

Question: Suppose you have identified a special subset of examples that might be causing a mismatch, and you mark that subset inside both the training set and the training-dev set. Explain how comparing the model's results on those two subsets can tell you whether collecting more examples of that type is a good idea.

Sample answer: First, measure the model on that same subset in both places. If the model does well on the subset within the training set but performs noticeably worse on that subset in the training-dev set, it suggests the model is not generalizing well to that kind of example. That pattern supports the idea that gathering additional data of that specific type would likely improve performance.

Key points:

  • Isolate the same subset in both the training set and the training-dev set
  • Compare the model's behavior on that subset across the two splits
  • If the training subset score is much better than the training-dev subset score, the mismatch hypothesis is strengthened and more data of that type may help

Rubric: The response must explain that the same subset should be evaluated in both the training and training-dev sets, and that strong training-subset performance combined with weak training-dev subset performance supports collecting more of that subset data.

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Updated 2026-08-12

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