Tag
selection-bias
- Sep 10, 2026 Why a Held-Out Test Set Cannot Be Reused What a test-set score actually estimates, how a second look at the same rows biases it upward, and the leakage paths that corrupt the number before any model is fitted. machine learning
- Dec 23, 2024 How Sampling Rules Decide Which Evidence Survives The telemetry left after an incident is a sample drawn by a rule chosen before the question was asked. Tail sampling, log thresholds, and retention turn the surviving data into a biased census. observability