LLM Fine-Tuning Validation Sample Size

Translate target precision requirements into the number of validation prompts needed after fine-tuning a language model.

Anticipated share of validation prompts the model will satisfy after fine-tuning.
Half-width of the confidence interval you require around the measured pass rate.
Accepted values: 80, 85, 90, 95, 98, or 99.
Enter the finite pool of eligible validation prompts to apply finite-population correction.

Statistical planning aid—validate sample size assumptions with a statistician when supporting regulated deployments or safety-critical launches.

Examples

  • 85% expected pass rate, 3% margin, 95% confidence, 2,500 prompt pool ⇒ Sample 544 prompts for the desired precision. After finite-population correction, sample 536 prompts.
  • 60% expected pass rate, 5% margin, 90% confidence, optional field blank ⇒ Sample 369 prompts for the desired precision.

FAQ

What if I need a different confidence level than those listed?

Use the closest value supported or extend the calculator with an inverse normal function to map your exact confidence requirement to a z-score.

How should I set the expected pass rate before the first release?

Base it on historical model evaluations, pilot study results, or a conservative midpoint (50%) when uncertainty is high to avoid undersampling.

Does this method handle multiple evaluation criteria simultaneously?

Apply the calculation independently to each binary criterion or use the lowest anticipated pass rate to size a shared sample that covers all checks.

Can I reuse the same prompts across iterations?

Only if exposure does not bias the model. For most fine-tuning programmes, reserve a pristine validation set and refresh it periodically to avoid leakage.

Additional Information

  • Result unit: number of validation prompts to evaluate in the hold-out sample.
  • Confidence level options align with common statistical z-scores for binomial proportions.
  • Finite-population correction reduces required samples when the validation pool is small relative to the estimate.

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