Description

This Standard specifies sampling plans and procedures that can be used to assess whether the quality level of an entity (lot, process, etc) conforms to a declared value.

This Standard is identical with and reproduced from ISO2859-4:2002.

Scope

The sampling plans have been devised so as to obtain a risk of less than 5% of contradicting a correct declared quality level. The risk is 10% of failing to contradict an incorrect declared quality level which is related to the limiting quality ratio. Sampling plans are provided corresponding to three levels of discriminatory ability.

In contrast to the procedures in the other parts of this Standard, the procedures in this part four are not applicable to acceptance assessment of lots. Generally, the balancing of the risks of reaching incorrect conclusions in assessment procedures will differ from the balancing in the procedures for acceptance sampling.

This part of the standard may be used for various forms of quality inspection in situations where objective evidence of conformity to some declared quality level is to be provided by means of inspection of a sample. The procedures are applicable to entities such as lots, process output, etc. that allow random samples of individual items to be taken from the entity.

The sampling plans provided in this part are applicable, but not limited, to inspection of a variety of products such as:

• end items;
• components and raw materials;
• operations;
• materials in process;
• supplies in storage;
• maintenance operations;
• data or records;
• administrative procedures.

The procedures are primarily intended to be used when the quantity of interest is the number or fraction of nonconforming items for which the inspected items are classified as conforming or nonconforming.

With minor changes, the procedures may also be used when the quantity of interest is the number of nonconformities or number of nonconformities per item.

The necessary changes are:

• replacement of “number of nonconforming items” by “number of nonconformities”;
• replacement of “percent nonconforming items” by “nonconformities per 100 items”.

In this case the values given in Tables 2 to 7 are only approximations.