Work out hallucination rate estimate instantly with clear inputs, formula shown and shareable results.
A hallucination rate measured on a sample is an estimate with uncertainty, and reporting it without a confidence interval invites false conclusions. The normal approximation gives a margin of error of z x sqrt(p(1-p)/n), so 26 flags in 400 reviews is about 6.5 percent plus or minus 2.4 points at 95 percent confidence — which cannot be distinguished from a 5 percent target.
Proportion confidence interval
p = flagged / sampled; margin = z x sqrt(p(1-p)/n); interval = p +/- margin
Roughly 2,000 to 4,000 at these rates. Detecting small differences in low-rate events needs large samples, which is why teams track trends rather than single measurements.
Define it before measuring: unsupported by the retrieved context, contradicted by it, or factually wrong about the world are three different metrics with very different rates.