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Relevance 7/10Data and MetricsAdvanced6 min read
Train-Test Contamination
Train-test contamination happens when overlapping information appears in both training and evaluation sets.
Why it matters for annotators
Contamination invalidates benchmark reliability.
Visual mental model
Split dataset -> overlap audit -> contamination removal.
Examples (bad vs good)
Scenario: Real annotation scenario involving Train-Test Contamination
Bad: Labeling quickly without applying project rubric.
Good: Applying rubric criteria, documenting rationale, and escalating uncertainty.
Common mistakes
- Skipping guideline details for edge cases.
- Applying inconsistent criteria across similar samples.
- Avoiding escalation even when uncertain.
Submission checklist
- Read the latest guideline update before each batch.
- Apply rubric dimensions explicitly in each decision.
- Escalate ambiguous items with concise rationale.