ISO/TC 213/WG 4 - Uncertainty of measurement and decision rules

This document defines the concepts of a reference temperature and the standard reference temperature and specifies the standard reference temperature value for the specification of geometrical and dimensional properties of an object. Some examples of geometrical and dimensional properties include size, location, orientation (including angle), form and surface texture of a workpiece. This document is also applicable to the definition of the measurand used in verification or calibration.

ISO 14253-1:2017 establishes the rules for verifying the conformity or nonconformity with a given tolerance for a characteristic of a workpiece (or a population of workpieces) or with a given maximum permissible errors for a metrological characteristic of a measuring equipment, including when the measured value falls close to the specification limits, taking measurement uncertainty into account. ISO 14253-1:2017 applies to specifications defined in general GPS standards (see ISO 14638), i.e. standards prepared by ISO/TC 213, including: - workpiece specifications and population specifications (usually given as an upper specification limit or a lower specification limit or both); - measuring equipment specifications (usually given as maximum permissible errors). ISO 14253-1:2017 only applies for characteristics and maximum permissible errors expressed as quantity values.

ISO 14253-5:2015 specifies concepts and terms for evaluating the uncertainties of the test values derived according to a test protocol agreed upon by the parties and relative to instrument indication(s), obtained in verification testing of GPS indicating measuring instruments. NOTE The uncertainty of the test values, referred to as test value uncertainty, is not to be confused with the measurement uncertainty associated with using that indicating measuring instrument to measure workpieces. The former only is covered in this part of ISO 14253; for guidance on the latter see the ISO/IEC Guide 98‑3 (GUM) and ISO 14253‑2. When a test of an indicating measuring instrument comprises several test values, some relative to the instrument indication and some to other metrological characteristics, this part of ISO 14253 is concerned with the uncertainty of the former only. This part of ISO 14253 does not provide guidelines to ensure the adequacy of a test protocol; rather, once a test protocol is given, it describes how to evaluate the consequent test value uncertainty.

ISO/TR 14253-6:2012 expands the scope of decision rules to industrial situations where the default rule of ISO 14253-1 might not be economically optimal. (ISO 14253-1 provides a default decision rule having a very high probability that a measured value resulting in product acceptance also yields a product with the corresponding measurand conforming to specifications.) ISO/TR 14253-6:2012 does not address how to determine the cost of correct decisions (accepting conforming workpieces or rejecting nonconforming workpieces) or incorrect decisions (rejecting conforming workpieces or accepting nonconforming workpieces) as this is a business concern. However, the terminology and requirements to communicate and implement the particular decision rules desired by an organization are provided along with examples to guide the reader.

ISO 14253-3:2011 provides guidelines and defines procedures for assisting the customer and supplier to reach amicable agreements on disputed measurement uncertainty statements regulated in accordance with ISO 14253-1, and so avoid costly and time-consuming disputes.

ISO 14253-2:2011 gives guidance on the implementation of the concept of the "Guide to the estimation of uncertainty in measurement" (in short GUM) to be applied in industry for the calibration of (measurement) standards and measuring equipment in the field of GPS and the measurement of workpiece GPS characteristics. The aim is to promote full information on how to achieve uncertainty statements and provide the basis for international comparison of measurement results and their uncertainties (relationship between purchaser and supplier). ISO 14253-2:2011 is intended to support ISO 14253-1. Both parts are beneficial to all technical functions in a company in the interpretation of GPS specifications [i.e. tolerances of workpiece characteristics and values of maximum permissible errors (MPEs) for metrological characteristics of measuring equipment]. ISO 14253-2:2011 introduces the Procedure for Uncertainty MAnagement (PUMA), which is a practical, iterative procedure based on the GUM for estimating uncertainty of measurement without changing the basic concepts of the GUM. It is intended to be used generally for estimating uncertainty of measurement and giving statements of uncertainty for: single measurement results; the comparison of two or more measurement results; the comparison of measurement results from one or more workpieces or pieces of measurement equipment with given specifications [i.e. maximum permissible errors (MPEs) for a metrological characteristic of a measurement instrument or measurement standard, and tolerance limits for a workpiece characteristic, etc.], for proving conformance or non-conformance with the specification. The iterative method is based basically on an upper bound strategy, i.e. overestimation of the uncertainty at all levels, but the iterations control the amount of overestimation. Intentional overestimation and not underestimation, is necessary to prevent wrong decisions based on measurement results. The amount of overestimation is controlled by economical evaluation of the situation. The iterative method is a tool to maximize profit and minimize cost in the metrological activities of a company. The iterative method/procedure is economically self-adjusting and is also a tool to change/reduce existing uncertainty in measurement with the aim of reducing cost in metrology (manufacture). The iterative method makes it possible to compromise between risk, effort and cost in uncertainty estimation and budgeting.

ISO 14253-4:2010 outlines the main assumptions behind the theoretically ideal decision rules established in ISO 14253-1. It discusses why these rules have to be the default rules and what considerations should be taken into account before applying different decision rules. ISO 14253-4:2010 applies to all specifications defined in general GPS standards (see ISO/TR 14638), i.e. standards prepared by ISO/TC 213, including workpiece specifications (usually given as specification limits), and measuring equipment specifications (usually given as maximum permissible errors).

ISO 14253-1:2013 establishes the rules for determining the conformity or nonconformity with a given tolerance for a characteristic of a workpiece (or a population of workpieces) or limits of maximum permissible errors for a metrological characteristic of a measuring equipment, taking into account the measurement uncertainty. These rules are different for tolerances to individual workpieces and tolerances to workpiece populations. It also gives rules on how to deal with cases where a clear decision (conformity or nonconformity with specification) cannot be taken, i.e. when the measurement result falls within the uncertainty range that exists around the specification limits. ISO 14253-1:2013 applies to specifications defined in general GPS standards (see ISO/TR 14538), i.e. standards prepared by ISO/TC 213, including: ? workpiece/population of workpieces specifications (usually given as an upper tolerance limit or a lower tolerance limit or both), and; ? measuring equipment specifications (usually given as maximum permissible errors). ISO 14253-1:2013 only applies for characteristics expressed as numerical quantity values.

ISO/TS 14253 provides guidelines and defines procedures for assisting the customer and supplier to reach amicable agreements on disputed measurement uncertainty statements regulated in accordance with ISO 14253-1, and so avoid costly and time-consuming disputes.