GB/T 2828.2-2008 Sampling procedures for inspection by attributes - Part 2: Sampling plans indexed by limiting quality (LQ) for isolated lot inspection
1 Scope
GB/T 2828.2 establishes an acceptance sampling inspection system by attributes indexed by limiting quality (LQ) for isolated lot (isolated series lot, isolated lot or single lot) when the switching rules given in GB/T 2828.1 are not applied. The sampling plans provided by this Part of GB/T 2828 are regarded as the supplement of GB/T 2828.1 and compatible with GB/T 2828.1.
The plans in this Part of GB/T 2828 are indexed by a preferred series of limiting qualities (LQ) with a consumer’s risk usually below 10 %, but only below 13 % in two circumstances. This method of indexing is more convenient than the special procedures for limiting quality protection in GB/T 2828.1.
Note: the plans in GB/T 2828.1 are indexed by a preferred series of AQL values and inspection levels. During the inspection of a continuing series of lots, the application of switching rules helps to ensure that the process average in that series of lots is kept below the specified AQL. Limiting quality does not have the same direct relationship with the process average.
This Part of GB/T 2828 is initially designed for the inspection of nonconforming items, which may also be used for the inspection of nonconformities per 100 items unless LQ values are overlarge. If this Part of GB/T 2828 does not apply, the consumers shall refer to the special procedures for limiting quality protection specified in 12.6.2 of GB/T 2828.1.
Alternative procedures are provided in this Part of GB/T 2828 to cater for two situations often met in practice:
a) Procedure A
Procedure A is to be used when the producer and consumer both wish to regard the lot in isolation. In other words, the uniqueness of lot lies in manufacturing only one lot according to its type.
b) Procedure B
Procedure B is to be used when the producer regards the lot as one of continuing series but the consumer considers the lot received in isolation. In other words, the consumers only receive one lot (or few lots) in the continuous series of lots. Procedure B is stated in Appendix A.
