This document provides guidance and procedures for assessing the conformity of an item (entity, object or system) with specified requirements. The item might be, for example, a gauge block, a grocery scale or a blood sample. The procedures can be applied where the following conditions exist: The procedures developed in this document can be used to realize an interval, called an acceptance interval, of permissible measured values of the property of interest. Acceptance limits can be chosen so as to balance the risks associated with accepting non-conforming items (consumer's risk) or rejecting conforming items (producer's risk). Two types of conformity assessment problems are addressed. The first is the setting of acceptance limits that will assure that a desired conformance probability for a single measured item is achieved. The second is the setting of acceptance limits to assure an acceptable level of confidence on average as a number of (nominally identical) items are measured. Guidance is given for their solution. This document contains examples to illustrate the guidance provided. The concepts presented can be extended to more general conformity assessment problems based on measurements of a set of scalar measurands. Documents such as references [19, 13] cover sector-specific aspects of conformity assessment. The audience of this document includes quality managers, members of standards development organizations, accreditation authorities and the staffs of testing and measuring laboratories, inspection bodies, certification bodies, regulatory agencies, academics and researchers.
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ISO/IEC Foreword
Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
3.1 Terms related to probability
3.2 Terms related to metrology
3.3 Terms related to conformity assessment
4 Conventions and notation
5 Tolerance limits and tolerance intervals
5.1 Conformity assessment measurements
5.2 Permissible and non-permissible values: tolerance intervals
6 Knowledge of the measurand
6.1 Probability and information
6.2 Bayes' theorem
6.3 Summary information
7 Probability of conformity with specified requirements
7.1 General rule for calculation of conformance probability
7.2 Conformance probabilities with normal PDFs
7.3 One-sided tolerance intervals with normal PDFs
7.4 Two-sided tolerance intervals with normal PDFs
7.5 Conformance probability and coverage intervals
7.6 Measurement capability index Cm
7.7 Measurement capability index and conformance probability
8 Acceptance intervals
8.1 Acceptance limits
8.2 Decision rule based on simple acceptance
8.3 Decision rules based on guard bands
9 Consumer's and producer's risks
9.1 General
9.2 PDFs for production process and measuring system
9.3 Possible outcomes of an inspection measurement with a binary decision rule
9.4 The joint PDF for Y and Ym
9.5 Calculation of global risks
Annex A Normal distributions (informative)
Annex B Prior knowledge of the measurand (informative)
Annex C Glossary of principal symbols (informative)
Annex ZZ Corresponding ISO/IEC Guides for the JCGM guidance documents for which their equivalents are not given in the text (informative)
ISO/IEC 17000:2004 Conformity assessment — Vocabulary and general principles.
ISO 3534-1:2006 Statistics — Vocabulary and symbols — Part 1: Probability and general statistical terms.
ISO 3534-2:2006 Statistics — Vocabulary and symbols - Part 2: Applied statistics.
ISO/IEC 17000:2004 Conformity assessment — Vocabulary and general principles.
ISO 3534-1:2006 Statistics — Vocabulary and symbols — Part 1: Probability and general statistical terms.
ISO 3534-2:2006 Statistics — Vocabulary and symbols - Part 2: Applied statistics.
JCGM 100:2008 Evaluation of measurement data — Guide to the expression of uncertainty in measurement (GUM).
JCGM 101:2008 Evaluation of measurement data — Supplement 1 to the "Guide to the expression of uncertainty in measurement" — Propagation of distributions using a Monte Carlo method.
JCGM 102:2011 Evaluation of measurement data — Supplement 2 to the "Guide to the expression of uncertainty in measurement" — Extension to any number of output quantities.
JCGM 200:2012 International vocabulary of metrology — Basic and general concepts and associated terms (VIM3).