What AQL actually does
An acceptance sampling plan selects a sample from a lot and applies acceptance and rejection rules. It manages the practical trade-off between inspecting everything and inspecting nothing. It does not mean that the accepted lot contains exactly the stated percentage of defects, and it cannot identify every defective unit.
The lot and the inspection level matter
Sample size depends on the lot size, inspection level and plan. Switching between normal, tightened and reduced inspection should follow defined rules and supplier history. If factories choose a convenient sample after seeing the lot, the statistical meaning is weakened. Keep the lot definition and random-selection method visible.
Separate critical, major and minor defects carefully
A cosmetic scratch and an unsafe earth connection do not belong in the same risk bucket. Safety-critical characteristics are usually better controlled through design, approved components, process controls and appropriate 100% production tests. Sampling can audit those controls, but a small final sample should not be the only barrier against a serious hazard.
Write the purchase agreement in plain language
State the applicable sampling standard, edition, lot definition, inspection level, AQL values, defect catalogue, reinspection rule and responsibility for rejected lots. ISO 2859-1:2026 sets out lot-by-lot attribute sampling procedures, while ISO 28590 introduces the wider ISO 2859 series and helps users select an inspection system.
- ISO 2859-1:2026: https://www.iso.org/standard/85464.html
- ISO 28590 introduction to the series: https://www.iso.org/standard/64622.html