ResearchResearch paperLarge Language Models · Training & Scaling · Evaluation & Benchmarks1 source · Oct 12, 2026

Mean Accuracy Is the Wrong Estimand for a Release Decision

Auditing $2\,124$ fine-tuned models across eleven language models, we show that shipping models based on mean accuracy violates a $10%$ deployment failure budget $48.0%$ of the time.

Key points

  • A release decision about a fine-tuned model is an operational commitment about the next rerun of its training recipe.
  • These target fundamentally different questions: release decisions depend on catastrophic tail risk, whereas standard evaluation reports only central tendency.
  • Common heuristics like $\bar b - 2σ$ prove equally dangerous: by underestimating variance on small samples, they become most permissive when evidence is weakest.
  • We introduce recipe cards, an evaluation framework that directly certifies rerun tail failure rates using exact finite-sample binomial bounds.

Sources (1)

  • [1]Mean Accuracy Is the Wrong Estimand for a Release Decision
    arXiv (AI, ML, NLP, CV, robotics, multi-agent) · Oct 12, 02:08 PM
    Auditing $2\,124$ fine-tuned models across eleven language models, we show that shipping models based on mean accuracy violates a $10%$ deployment failure budget $48.0%$ of the time.
    A release decision about a fine-tuned model is an operational commitment about the next rerun of its training recipe.

Extractive summary: sentences quoted from the sources.

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