Work out human review sample size instantly with clear inputs, formula shown and shareable results.
Sample size for estimating a proportion is z^2 p(1-p) / e^2, then reduced by the finite-population correction when the sample is a meaningful fraction of the whole. Note what is absent: population size barely matters. Reviewing 1,000 items gives about the same precision whether the population is 100,000 or 100 million, which is why audit samples are far smaller than intuition suggests.
Sample size for a proportion
n0 = z^2 p(1-p) / e^2; n = n0 / (1 + (n0 - 1) / N)
Use 50 percent. It maximises p(1-p) and therefore gives the largest, safest sample size.
Only through the correction term, which is negligible once the population is more than about 20 times the sample. Precision is driven almost entirely by sample size.