Sampling procedures for inspection by attributes—Part 5:System of sequential sampling plans indexed by acceptance quality limit(AQL)for lot-by-lot inspection
1 Scope
This part of GB/T 2828 specifies sequential sampling schemes that supplement the GB/T 2828.1 acceptance sampling system for inspection by attributes.
The GB/T 2828.1 acceptance sampling system is indexed in terms of the acceptance quality limit (AQL). Its purpose is to induce a supplier, 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.
The sampling schemes defined in this part of GB/T 2828 are applicable, but not limited, to the inspection of:
——end items,
——components and raw materials,
——operations,
——materials in process,
——supplies in storage,
——maintenance,
——data or records, and
——administrative procedures.
These schemes are designed to be applied to a continuing series of lots, that is, a series long enough to permit the switching rules in 10.3 to be applied. These switching rules provide
a) enhanced protection to the consumer (by means of tightened sampling inspection criteria or discontinuation of sampling inspection) should deterioration in quality occur,
b) an incentive, at the discretion of the responsible authority, to reduce inspection costs (by means of reduced sampling inspection criteria) should consistently good quality be demonstrated over time.
The individual sampling plans are not designed to be used outside of the schemes in which they are presented. Where lots are produced in isolation or in a series too short for this part of GB/T 2828 to apply, the user is advised to consult GB/T 2828.2 or GB/T 8051 for appropriate sampling plans.
2 Normative References
The following document is essential for the application of this Standard. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) is applicable to this document.
GB/T 2828.1-2003 Sampling procedures for inspection by attributea-Part1:Sampling schemes indexed by acceptance quality limit(AQL) for lot-by-lot inspection (ISC)2859-1:1999, IDT)
GB/T 3358.2-2009 Statistics—Vocabulary and symbols—Part 2:Applied statistics (ISO 3534-2:2006, IDT)
Contents
Foreword
1 Scope
2 Normative References
3 Terms and definitions
4 Symbols and abbreviated terms
5 Expression of nonconformity
5.1 General
5.2 Classification of nonconformities
6 Acceptance quality limit (AQL)
6.1 Use and application
6.2 Specifying AQLs
6.3 Preferred AQLs
7 Submission of product for sampling
7.1 Formation of lots
7.2 Presentation of lots
8 Acceptance and non-acceptance
8.1 Acceptability of lots
8.2 Disposition of non-acceptable lots
8.3 Nonconforming items
8.4 Classes of nonconformities or nonconforming items
8.5 Special reservation for critical classes of nonconformities
8.6 Resubmitted lots
9 Drawing of samples
9.1 Sample selection
9.2 Time for drawing the samples
10 Normal, tightened and reduced inspection
10.1 Start of inspection
10.2 Continuation of inspection
10.3 Switching rules and procedures (see Figure 1)
10.4 Discontinuation of inspection
11 Sampling plans
11.1 Inspection level
11.2 Sample size code letters
11.3 Obtaining a sampling plan
11.4 Operation of a sequential sampling plan
11.5 Numerical examples
12 Determination of acceptability
12.1 Inspection for nonconforming items
12.2 Inspection for nonconformities
13 Further information
13.1 Operating characteristic (OC) curves
13.2 Process average
13.3 Use of individual plans
14 Tables
Annex A (normative) Sampling plans for normal inspection
Annex B (normative) Sampling plans for tightened inspection
Annex C (normative) Sampling plans for reduced inspection
Annex D (informative) Average sample numbers for sequential sampling plans
