AQLregels

AQLregels are rules used in acceptance sampling to decide whether a batch of goods should be accepted or rejected based on the Acceptance Quality Level (AQL). The AQL represents the largest percentage of defects that is considered acceptable for a given lot under defined conditions. The rules specify, for a given lot size, how many units to inspect (the sample) and the maximum number of defects that may be found in the sample (the acceptance number). If the defect count in the sample is at or below the acceptance number, the lot is accepted; otherwise it is rejected or sent for rework.

Standards and practice: The AQL concept is standardized in international standards such as ISO 2859-1 and ANSI/ASQ Z1.4, with historical roots in MIL-STD-105E. In practice, organizations select an inspection level and AQL values for different defect categories, and the specific sampling plan depends on the lot size and the chosen standard. Defect categories commonly used are critical, major, and minor, though some applications treat only major and minor or use separate criteria for each category.

Process: The typical process involves determining the lot size, selecting an AQL level and inspection level, consulting the sampling plan, inspecting a representative sample, counting defects, and comparing the results with the plan’s acceptance numbers to decide whether to accept or reject the lot. If rejected, actions may include rework, return, or a supplier corrective action.

Limitations: AQL-based sampling is probabilistic and does not guarantee defect-free lots. Effectiveness depends on proper sampling, defect detection, and appropriate choice of AQL values according to product criticality and risk.