AQL is an indexing parameter for acceptance-sampling plans over a continuing series of lots. It is not “the percentage defective allowed in this lot” or permission to ship defects. ISO 2859-1:2026 uses lot size, inspection level, AQL and normal/tightened/reduced status to determine sample size and acceptance/rejection numbers.
Values in this article support engineering screening during design review, RFQ and prototyping. They do not replace formal calculations, material data sheets, qualified procedures or contractual standards.
CORRECT WORKFLOW
1. Classify critical, major and minor defects with objective criteria. Critical defects commonly use zero acceptance, though Ac=0 still does not mean zero risk. 2. Define a lot as completed, traceable product made under common conditions; never split a problem lot to obtain a more favorable plan. 3. Use the contractual standard edition: lot size and inspection level give a code letter; the AQL table then gives n, Ac and Re. Do not copy a fixed “inspect 80” rule online. 4. Sample randomly across boxes, pallets, times and machines; top-layer convenience sampling is not random. 5. Handle a rejected lot under predefined return, 100% screening, rework or concession rules; resubmission after screening must be traceable.
STATE THE RISKS
Acceptance sampling has producer’s risk α (rejecting a good lot) and consumer’s risk β (accepting a bad lot). The plan’s OC curve shows acceptance probability at different true defect levels; AQL alone does not show the full risk. For isolated lots consider ISO 2859-2:2020. Where measurable continuous data meet assumptions, ISO 3951-1:2022 variables sampling retains more information than reducing dimensions to pass/fail.
PRACTICAL BOUNDARIES
AQL supports shipment acceptance; it does not replace SPC, process audits, mistake-proofing or 100% automated checks for critical safety features. A systemic error—wrong material, revision or missing operation—should trigger quarantine and investigation even below Re, because the random-defect model no longer applies. ======================================================================