Case context: A team uses its test set to estimate the final performance of a system, but the team does not feel confident in the estimate.

Question: Based only on the test-set sizing principle, what should the team diagnose or decide?

Sample answer: The team should diagnose that the test set has not yet demonstrated that it is big enough for its purpose. The relevant decision criterion is whether the test set supports a confident estimate of the system's final performance.

Key points:

• The current estimate is not confident.
• A confident final-performance estimate is the sizing objective.
• The test set has not satisfied the stated criterion for being big enough.
• The diagnosis concerns estimation confidence, not necessarily performance quality.

Rubric: The response should connect the lack of confidence directly to the test set's sizing criterion without claiming that the system's performance itself is necessarily poor.