Standards Development

Scope

This part of ISO 2859 specifies sampling schemes indexed by acceptance quality limit (AQL) for inspection by attributes.

Its purpose is to induce 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 part of ISO 2859 are applicable, but not limited, to inspection of

— end items, such as complete products or sub-assemblies,

— components and raw materials,

— operations,

— materials in process,

— supplies in storage,

— maintenance operations,

— data or records, and

— administrative procedures.

1.1 Continuous Inspection

These schemes shall 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) a protection to the consumer (by means of a switch to tightened inspection or discontinuation of sampling inspection) should a deterioration in quality be detected.

b) 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 (see 1.2) should consistently good quality be achieved.

1.2 Skip-lot Inspection 

This part of ISO 2859 also specifies optional skip-lot sampling procedures 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 ISO 2859-1 to the random selection of lots. The skip-lot sampling procedures specified in this part of ISO 2859 are applicable to, but not limited to, inspection of

— end items, such as complete products or sub-assemblies,

— components and raw materials,

— operations,

— materials in process,

— supplies in storage,

— maintenance operations,

— data or records, and

— administrative procedures.