IEC GUIDE 98-3 Uncertainty of measurement Part 3: Guide to the expression of uncertainty in measurement (GUM:1995) Incertitudedemesure- Partie 3: Guide pourI'expression de l'incertitude de mesure (GUM:1995) First edition 2008 Intemational Organization for Standardization LicsSQEGns2008standardizaton 595617 Not for Resale, 2015/5/20 03:02:39 ISO/IECGUIDE98-3:2008(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The IsO Central Secretariat accepts no liability in this area. Adobe is a trademark of Adobe Systems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by IsO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. COPYRIGHTPROTECTEDDOCUMENT ISO/IEC2008 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either isO at the address below or ISO's member body in the country of the requester. ISO copyright office Casepostale56.CH-1211Geneva20 Tel:+ 4122749 01 11 Fax + 41 22 749 09 47 E-mail [email protected] Web www.iso.org Published in Switzerland Licensee-Zheljang nsttute of Standardiza JS/EC 2008 - All rights reserved Not for Resale, 2015/5/20 03:02:39 ISO/IECGUIDE98-3:2008(E) Contents Page Preliminary . V Foreword. .vi 0 Introduction. vii 1 Scope... 2 Definitions.. 2.1 General metrological terms... 2.2 The term “"uncertainty" 2.3 Terms specific to this Guide. 3 Basic concepts 3.1 Measurement. 3.2 Errors,effects,and corrections 3.3 Uncertainty... 3.4 Practical considerations. 4 Evaluating standard uncertainty.. 4.1 Modelling the measurement....... .8 4.2 Type A evaluation of standard uncertainty.... 4.3 Type B evaluation of standard uncertainty. 11 4.4 Graphical illustration of evaluating standard uncertainty 15 5 Determining combined standard uncertainty... .18 5.1 Uncorrelated input quantities ... .18 5.2 Correlated input quantities... 21 6 Determining expanded uncertainty 6.1 Introduction..... 23 6.2 Expanded uncertainty.. 23 6.3 Choosing a coverage factor.. Reporting uncertainty. 24 7.1 General guidance 24 7.2 Specific guidance... 25 8 Summary of procedure for evaluating and expressing uncertainty .27 Annex ARecommendations of Working Group and CiPM .28 A.1 RecommendationINC-1(1980). .28 A.2 Recommendation 1 (Cl-1981).... A.3 Recommendation 1 (Cl-1986)... .29 Annex B General metrological terms B.1 Source of definitions... 31 B.2 Definitions..... 31 Annex C Basic statistical terms and concepts. .39 C.1 Source of definitions... ..39 C.2 Definitions... .39 C.3 Elaboration oftermsand concepts. 45 Annex D “True" value, error, and uncertainty.... .49 D.1 D.2 The realized quantity... .49 D.3 The "true" value and the corrected value ... 49 D.4 50 mational Oorganization@ SQ/EGo.2008 -All rights reserved LicenseeZhejiang Institute of Standardization 5956617 ili Not for Resale, 2015/5/20 03:02:39 license from IHS ISO/IECGUIDE98-3:2008(E) D.5 Uncertainty .51 D.6 Graphical representation. .51 AnnexEMotivation and basisfor Recommendation INC-1 (1980) .54 E.1 "Safe","random",and"systematic" ..54 E.2 Justificationforrealisticuncertaintyevaluations... ...54 E.3 Justificationfortreatingalluncertaintycomponentsidentically .55 E.4 Standard deviations as measures of uncertainty.... ..58 E.5 A comparison of two views of uncertainty ....