The quality level used to index acceptance sampling plans for a continuing series of lots, not a guaranteed defect rate in each lot.
AQL indexes a sampling scheme for a continuing series of lots. Agree the standard, inspection level, inspection mode and AQL before selecting the sample.
Select the plan before inspection
Use the lot size and inspection level to find the code letter, then follow the applicable table to obtain the sample size and acceptance and rejection numbers. Do not multiply the AQL percentage by the sample size to calculate the acceptance number.
Understand the decision
Compare the observed count with the selected plan. Specify whether you count nonconforming units or nonconformities. Sampling can accept a poor lot or reject a good lot; an accepted sample does not prove every unit is defect-free. Agree separate rules for critical defects.
Key takeaways
- AQL is not the maximum defect percentage allowed in each lot.
- Use the complete sampling scheme, including applicable switching rules.