1 Scope
This document specifies an acceptance sampling system of single, double, and multiple sampling plans for inspection by attributes. This document specifies sampling schemes indexed by acceptance quality limit (AQL) for inspection by attributes.
Its purpose is to incentivize the producer through the economic and psychological pressure of lot non-acceptance to maintain a process average at least as good as the specified acceptance quality limit, while at the same time providing an upper limit for the risk to the consumer of accepting the occasional poor lot.
Sampling schemes designated in this document are applicable, but not limited, to inspection of
items, such as complete products, sub-assemblies or individual components,
operations,
materials in process,
supplies in storage,
maintenance operations,
data or records, and
administrative procedures.
1.1 Continuous inspection
These schemes are intended to be used for a continuing series of lots, that is, a series long enough to allow the switching rules (9.3) to be applied. These rules provide:
a protection to the consumer (by means of a switch to tightened inspection or discontinuation of sampling inspection) if a deterioration in quality be detected.
an incentive (at the discretion of the responsible authority) to reduce inspection costs (by means of a switch to reduced inspection or the adoption of skip-lot sampling inspection (see 1.2)) if consistently good quality be achieved.
1.2 Skip-lot inspection
This document also specifies optional skip-lot sampling inspection procedures (see 9.5) for acceptance inspection by attributes. The purpose of these procedures is to provide a way of reducing the inspection effort on products of high quality submitted by a producer who has a satisfactory quality assurance system and effective quality controls. The reduction in inspection effort is achieved by determining at random, with a specified probability, whether a lot presented for inspection will be accepted without inspection. This procedure extends the principle of the random selection of sample items already applied in this document to the random selection of lots. The skip-lot sampling inspection procedures specified in this document are applicable to, but not limited to, inspection of the items detailed in 1.1.