GUIDE 33 Third edition 2015-02-01 Reference materials Good practice in using reference materials Materiaux de reference - Bonne pratique d'utilisation des materiauxderéférence Referencenumber ISO GUIDE 33:2015(E) ISO @ISO2015 IS0GUIDE33:2015(E) COPYRIGHTPROTECTEDDOCUMENT iS02015 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form orby any means, electronic or mechanical, including photocopying,or posting on the internet or an intranet,without prior therequester. ISO copyrightoffice Case postale 56. CH-1211 Geneva 20 Tel.+41227490111 Fax +41227490947 E-mail copyright@iso.org Webwww.iso.org Published in Switzerland i @Is02015-Allrightsreserved IS0 GUIDE33:2015(E) Contents Page Foreword V Introduction.. ..vi 1 Scope. .1 2 Normative references. .1 3 Terms and definitions .2 4 Symbols .3 5 Conventions .3 6 RMs and their role in measurement 4 6.1 CommonapplicationsofRMs 4 6.2 Property values 6.2.1 General 6 6.2.2 Specification oftheproperty 6.3 Uncertainty statement. 6 6.4 Traceability statement. 8 7 Handling of RMs and CRMs .9 8 Assessment of precision.. 9 8.1 General .9 8.2 Numberof replicate measurements .9 8.3 RequirementswithrespecttotheRM 10 8.4 Measurement 11 8.5 Data treatment 11 8.6 Calculationandassessmentofprecision 12 9 Bias assessment. 12 9.1 General.. 12 9.2 Approach to bias checking. 13 9.3 Utilizing bias data... 13 10 Calibration .14 10.1 General. .14 10.2 Establishing metrological traceability 15 10.3 Calibration models.. 15 11 Assigningvaluestoothermaterials .15 11.1 General. .15 11.2 Pure materials 16 11.3 Gravimetry and volumetry .17 12 Conventional scales .18 12.1 General. 18 12.2 pH-scale. 19 12.3 Octane number .19 13 Selection of CRMs and RMs .20 13.1 General. 20 13.2 Selection of a CRM.. 20 13.3 Selection of RMs.. 23 13.4 Relevancetothemeasurementsystem. 23 Annex A (informative) Key characteristics of a reference material with respect its commonapplications .25 Annex B (informative) Calibration models and associated uncertainty models .26 AnnexC (informative)Decisionerrors .29 IS02015-Allrightsreserved iii