How Many Samples Does It Take to Trust a Batch?

October 12, 2026 · 7 min read

You have 1,000 items, but testing every one of them is expensive. How many should you randomly inspect: 10, 100, or half the batch?

There is no universal answer based on population size alone. As the NIST/SEMATECH e-Handbook explains^[1], sample-size planning depends on the statistical objective and precision requirements. The useful question is: How many items do I need to estimate a proportion with a chosen level of precision? Under common assumptions, the answer is 278—not an arbitrary percentage of the batch.