ISO IEC Guide 98-4-2012 PDF

Full title and description

ISO/IEC Guide 98-4:2012 — Uncertainty of measurement — Part 4: Role of measurement uncertainty in conformity assessment. Guidance for the use of measurement results and their associated uncertainties when deciding whether an item meets specified requirements; includes procedures to set acceptance limits and to balance producer's and consumer's risks in conformity assessment based on measurement.

Abstract

This guide explains how measurement uncertainty should be taken into account in conformity assessment decisions. It provides methods to derive acceptance intervals for measured quantities, shows how those intervals relate to tolerance or specification limits, and describes approaches to set acceptance limits so as to control the risks of accepting non-conforming items (consumer's risk) and rejecting conforming items (producer's risk). The guide addresses both single-item decisions and averaged confidence across batches of nominally identical items and includes worked examples to illustrate the procedures.

General information

• Status: Published (confirmed on review).
• Publication date: 19 November 2012 (Edition 1, 2012); corrected language edition published subsequently (French corrected version issued 2017) and the document was confirmed at review in 2021.
• Publisher: ISO and IEC (joint publication as an ISO/IEC Guide).
• ICS / categories: 17.020 — Metrology and measurement in general.
• Edition / version: Edition 1 (2012).
• Number of pages: 49 pages.

Scope

Provides guidance and procedures for assessing conformity of an item whose characteristic can be represented by a single scalar measurand, when measurement results are available and uncertainty can be expressed according to the principles of the Guide to the Expression of Uncertainty in Measurement (GUM). The guide is limited to cases where permissible values are specified by one or two tolerance limits and where the measurement outcome and uncertainty permit probabilistic description (probability density or distribution functions, or an estimate plus a coverage interval). It develops methods for establishing acceptance intervals and for choosing acceptance limits to manage producer's and consumer's risks in conformity assessment.

Key topics and requirements

• Role of measurement uncertainty in making conformity decisions for scalar measurands.
• Definition and construction of acceptance intervals consistent with specification/tolerance limits.
• Procedures to set acceptance limits that achieve a desired conformance probability for a single measured item.
• Methods to set acceptance limits that provide acceptable average confidence across multiple nominally identical items (batch/lot considerations).
• Quantification and balancing of consumer's risk (accepting non‑conforming items) and producer's risk (rejecting conforming items).
• Examples and numerical illustrations to demonstrate application of the methods.
• Assumptions and limitations: scalar measurand focus, requirement for a probabilistic description of measurement knowledge (consistent with GUM principles).

Typical use and users

Used by testing and calibration laboratories, inspection and certification bodies, accreditation authorities, regulatory agencies, quality managers and statisticians involved in conformity assessment. Practical users include laboratories creating decision rules for pass/fail testing, standard developers and accreditation assessors who need to justify how uncertainty is considered in conformity statements, and industry practitioners setting acceptance criteria for product inspection and quality control.

Related standards

Closely related to ISO/IEC Guide 98-3 (the Guide to the Expression of Uncertainty in Measurement — the GUM) and to JCGM documents that elaborate GUM principles. Also used alongside conformity-assessment standards such as ISO/IEC 17025 (general requirements for the competence of testing and calibration laboratories) and ISO/IEC 17000 series (fundamentals of conformity assessment), and with sector-specific measurement and test standards that require explicit treatment of uncertainty in decision rules.

Keywords

measurement uncertainty, conformity assessment, acceptance interval, acceptance limits, producer's risk, consumer's risk, GUM, metrology, decision rule, tolerance limits, accreditation

FAQ

Q: What is this standard?

A: ISO/IEC Guide 98-4:2012 is a guidance document that explains how to incorporate measurement uncertainty into conformity assessment decisions for scalar measurands; it provides procedures to derive acceptance intervals and to set acceptance limits that control risks in pass/fail decisions.

Q: What does it cover?

A: It covers methods for using measurement results together with their uncertainties to decide whether an item meets specified requirements, including procedures for single-item decisions and for assuring levels of confidence across multiple items, and it illustrates the approaches with examples.

Q: Who typically uses it?

A: Quality and metrology professionals: testing and calibration laboratories, certification and inspection bodies, accreditation authorities, regulators, standards developers, and researchers concerned with applying uncertainty information to conformity decisions.

Q: Is it current or superseded?

A: The edition was published in 2012 (Edition 1). The document has been maintained (language corrections issued subsequently) and confirmed at review; users should check the latest status with their national standards body or the publishers for any amendments or newer editions.

Q: Is it part of a series?

A: Yes. It is Part 4 in the ISO/IEC Guide 98 series on uncertainty of measurement (the series includes the GUM and related parts) and is intended to be used together with Guide 98-3 (GUM) and associated JCGM documents that provide the underlying uncertainty framework.

Q: What are the key keywords?

A: Measurement uncertainty, conformity assessment, acceptance interval, decision rule, producer's risk, consumer's risk, GUM, metrology.