Question: In a concise analytical response, explain why adding training data cannot by itself reach the desired performance when training error already exceeds that level.

Sample answer: When training error is already higher than the desired performance level, adding more training data cannot move it down to that level because training error can only stay the same or get worse as data is added. The dev-error curve is usually higher than the training-error curve. Therefore, if training error cannot reach the desired level through more data alone, there is almost no way for dev error to do so.

Key points:

• Training error begins above the desired performance level.
• Training error can only stay the same or rise as data is added.
• Dev error is usually higher than training error.
• The two observations imply that dev error cannot be expected to reach the desired level through more data alone.

Rubric: A strong response identifies the initial relationship between training error and desired performance, states both source observations, and connects them logically to the conclusion that more data alone is insufficient.