ISO 3951-1-2022 PDF

Full title and description

Sampling procedures for inspection by variables — Part 1: Specification for single sampling plans indexed by acceptance quality limit (AQL) for lot-by-lot inspection for a single quality characteristic and a single AQL. This international standard specifies single-sample plans and acceptance criteria for continuous, measurable quality characteristics under lot-by-lot inspection conditions.

Abstract

Specifies single sampling plans indexed by AQL for lot-by-lot inspection where a single continuous quality characteristic is measured, production is statistically controlled and the characteristic is approximately normally distributed. The standard covers single and double specification-limit cases (lower L, upper U or both) and indicates how to treat combined control when both limits apply.

General information

• Status: Published.
• Publication date: August 2022.
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 03.120.30 (Application of statistical methods).
• Edition / version: Edition 3 (2022).
• Number of pages: 107 pages (as published by ISO).

Scope

Applies to lot-by-lot inspection of discrete products from a single producer and process where one continuous quality characteristic x is measured. Assumes production is under statistical control and x is approximately normally distributed. Addresses cases with a lower specification limit, an upper specification limit, or both; gives sampling plans indexed by a single AQL and guidance for combined control when two limits are equally important.

Key topics and requirements

• Single sampling plans indexed by Acceptance Quality Limit (AQL) for variables inspection.
• Assumptions: measurable continuous characteristic, statistical control, approximate normality of the characteristic.
• Acceptance criteria based on comparison to lower and/or upper specification limits (L, U) and on estimated percent nonconforming.
• Procedures for combined control when both specification limits apply (single AQL applied to combined out-of-spec percentage).
• Tables and rules for selecting sample sizes and acceptance/rejection limits for lot sizes and AQLs.
• Guidance consistent with other sampling standards and with use of switching rules where appropriate.

Typical use and users

Used by quality engineers, inspection planners, production managers, conformity assessment bodies and contract writers who need statistically sound, AQL-indexed single-sample plans for continuous measurements. Typical applications include incoming inspection, final product inspection and contractual acceptance testing where a single measurable characteristic is the focus of accept/reject decisions.

Related standards

ISO 3951-1 is part of the ISO 3951 family on inspection by variables (see ISO 3951-2 for multi-characteristic/general specifications). It is commonly used alongside ISO 2859 (sampling by attributes) and other ISO/TC 69 statistical-method standards. Specific related items include ISO 3951-2 (general specification for single sampling plans of independent quality characteristics) and ISO 2859-1 (sampling procedures for inspection by attributes).

Keywords

Acceptance sampling, AQL, sampling by variables, lot-by-lot inspection, sample size, acceptance criteria, specification limits, statistical quality control, ISO 3951.

FAQ

Q: What is this standard?

A: An ISO international standard (ISO 3951-1:2022) that specifies single-sampling plans for inspection by variables indexed by an Acceptance Quality Limit (AQL).

Q: What does it cover?

A: It covers single-sample AQL-based plans for a single continuous quality characteristic under lot-by-lot inspection, including handling of lower and/or upper specification limits and combined control when both limits apply.

Q: Who typically uses it?

A: Quality assurance and production personnel, inspection bodies, contract authors, and statisticians who need to design or implement AQL-indexed sampling for measurable characteristics. It is used where measurement data (variables) are available rather than attribute pass/fail counts.

Q: Is it current or superseded?

A: Current — ISO 3951-1:2022 (Edition 3, published August 2022) supersedes earlier editions (for example ISO 3951-1:2013).

Q: Is it part of a series?

A: Yes — ISO 3951 is a multi-part series on sampling procedures for inspection by variables; Part 2 and other related parts cover broader or complementary sampling topics. It is often used together with the ISO 2859 attribute-sampling standard family.

Q: What are the key keywords?

A: AQL, sampling by variables, acceptance sampling, lot-by-lot inspection, specification limits, statistical quality control, ISO 3951.