(1) In a continuing series of lots, a quality level that, for the purpose of sampling inspection, is the limit of a satisfactory process average.
(2) The maximum percentage or proportion of non-conformities in a lot or batch that can be considered satisfactory as a process average.
The acceptable quality level (AQL) or acceptable quality limit is the worst tolerable process average in percentage or ratio, that is still considered acceptable. Closely related terms are the rejectable quality limit and level (RQL). In a quality control procedure, a process is said to be at an acceptable quality level if the appropriate statistic used to construct a control chart does not fall outside the bounds of the acceptable quality limits. Otherwise, the process is said to be at a rejectable control level.
An acceptable quality level is an inspection standard describing the maximum number of defects that could be considered acceptable during the random sampling of an inspection. The defects found during inspection are sometimes classified into three levels: critical, major and minor. Critical defects are those that render the product unsafe or hazardous for the end user or that contravene mandatory regulations. Major defects can result in the product's failure, reducing its marketability, usability or saleability. Lastly, minor defects do not affect the product's marketability or usability, but represent workmanship defects that make the product fall short of defined quality standards. Different companies maintain different interpretations of each defect type. In order to avoid argument, buyers and sellers agree on an AQL standard, chosen according to the level of risk each party assumes, which they use as a reference during pre-shipment inspection.