Question: Respond in one to three sentences by relating performance on data the model has already learned from to performance on new data.

Sample answer: A model is judged first on the data it was trained with, because that shows whether it has learned the task at all. If it does not do well on familiar training examples, there is little reason to expect it to do well on new validation or test examples, which are usually harder.

Key points:

• Training examples are the data used to fit the model.
• Results on validation or test data are typically lower than training results.
• Strong learning on the training set should come before expecting good generalization.

Rubric: The response should refer to training examples as the data already seen, note that validation or test results are usually worse, and explain that strong training performance should come first.