ISO 3951-2-2013 (2016) PDF

Full title and description

Sampling procedures for inspection by variables — Part 2: General specification for single sampling plans indexed by acceptance quality limit (AQL) for lot-by-lot inspection of independent quality characteristics. Second edition, published 2013 with a corrected version issued in December 2016; provides general rules and tables for single-sample plans by variables used to decide lot acceptability based on an AQL index.

Abstract

ISO 3951-2:2013 specifies an acceptance-sampling system of single sampling plans for inspection by variables, indexed in terms of the acceptance quality limit (AQL). The methods are intended to give a high probability of acceptance for lots of acceptable quality and a high probability of rejection for inferior lots, and include switching rules to move between normal, tightened or reduced inspection. The part is technical and intended for users familiar with variable-based sampling (an introductory treatment is given in ISO 3951-1).

General information

• Status: Published (current edition: 2).
• Publication date: 2013-09 (corrected version published 2016-12).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 03.120.30 (Application of statistical methods / acceptance sampling).
• Edition / version: 2nd edition (2013), corrected 2016.
• Number of pages: 86 (ISO published version).

Scope

Applies to lot-by-lot inspection of discrete products where quality characteristics are measurable on a continuous scale and independent of one another (or treated as independent). It provides general specifications for single sampling plans indexed by AQL for one or more independent quality characteristics, including treatment of single and double specification limits, combined/separate/complex control for multiple characteristics, and guidance on switching rules for tightened or reduced inspection. Intended for use on a continuing series of lots supplied by one producer and production process.

Key topics and requirements

• Definition and construction of single sampling plans for variables indexed by AQL.
• Switching rules (normal, tightened, reduced inspection) to protect consumers and reward consistent quality.
• Treatment of single and double specification limits; combined, separate and complex control for multiple characteristics.
• Assumptions on distribution (approximate normality), measurement error, and independence of characteristics.
• Tables and procedures for deciding sample sizes and acceptance criteria from measured data (including K-factor considerations).

Typical use and users

Used by quality engineers, statisticians, inspection planners, and procurement/specification authors in manufacturing and supply-chain organizations who need statistically based lot acceptance criteria for measurable product characteristics. Typical applications include incoming inspection, production lot release, supplier agreements and contract inspection where AQL-indexed variable sampling is preferred over attribute sampling.

Related standards

Belongs to the ISO 3951 series (sampling by variables). Closely related documents include ISO 3951-1 (single sampling plans for a single characteristic and single AQL), ISO 3951-3 (double sampling schemes), ISO 3951-4 (procedures for assessment of declared quality levels) and ISO 3951-5 (sequential sampling plans). It is also used alongside attribute-sampling standards such as ISO 2859 (AQL attribute sampling) and general statistical vocabulary standards (ISO 3534).

Keywords

AQL, acceptance sampling, sampling by variables, single sampling plan, lot-by-lot inspection, switching rules, quality control, statistical inspection, K-factor, specification limits.

FAQ

Q: What is this standard?

A: ISO 3951-2:2013 is the international standard that gives the general specification for single sampling plans by variables indexed to an acceptance quality limit (AQL) for lot-by-lot inspection of independent quality characteristics.

Q: What does it cover?

A: It covers construction and application of single-sample variable sampling plans (including tables and acceptance criteria), switching rules between inspection levels, treatment of single and double specification limits, and guidance for multiple independent characteristics under the assumptions required for variable sampling.

Q: Who typically uses it?

A: Quality engineers, production and inspection planners, statisticians, conformity assessment bodies and procurement/specification writers who require variable-based AQL sampling plans for measurable product characteristics.

Q: Is it current or superseded?

A: ISO 3951-2:2013 (corrected in December 2016) is the current published edition for part 2. (Note: other parts of the ISO 3951 series have seen updates — for example ISO 3951-1 was revised in 2022 — but as of the current published record ISO 3951-2 remains the 2013 edition with 2016 corrections.)

Q: Is it part of a series?

A: Yes — it is Part 2 of the ISO 3951 series (Sampling procedures for inspection by variables), which includes Parts 1, 2, 3, 4 and 5 (and related national/adopted variants).

Q: What are the key keywords?

A: AQL; acceptance sampling; sampling by variables; single sampling plan; lot-by-lot inspection; switching rules; specification limit; K-factor; statistical quality control.