ISO INTERNATIONAL STANDARD 12491 First edition 1997-05-01 Statistical methods for quality control of building materials and components Methodes statistiques de controle de la qualite des materiaux et elements de construction This material is reproduced from Iso documents under International Organization for Standardization (IsO) Copyright License number IHS/IcC/1996. Not for resale. No part of these ISo documents may be reproduced in any form, electronic retrieval system or otherwise, except as allowed in the copyright law of the country of use, or with the prior written consent of Iso (Case postale 56, 1211 Geneva 20, Switzerland, Fax +41 22 734 10 79), IHS or the ISO Licensor's members. ISO Reference number ISO 12491:1997(E) Copyightltematioal Organizationfor Standardization No reproduction or networking permited without license from IHS Not for Resale ISO 12491:1997(E) Contents Page 1 Scope 1 2 Normative references 1 3 Definitions 1 4 Population and sample 8 4.1 General 8 4.2 Normal distribution 8 4.3 Log-normal distribution 6 4.4 Normality tests ... 9 5 Methods of statistical quality control 9 5.1 Quality requirements 9 5.2 Basic statistical methods 10 5.3 Bayesian approach 10 5.4 Additional methods 12 Estimation and tests of parameters 12 6.1 Principles of estimation and tests 12 6.2 Estimation of the mean 13 6.3 Estimation of the variance. 13 6.4 Comparison of means 14 6.5 Comparison of variances .. 15 6.6 Estimation of fractiles.. 15 6.7 Prediction of fractiles using the Bayesian approach 16 Sampling inspection 18 7.1 Variables and attributes 18 7.2 Inspectionofanisolatedlot 18 7.3 Sampling inspection by variables: known... 19 7.4 Sampling inspection by variables: unknown 20 7.5 Sampling inspection by attributes 20 Annex A Bibliography 27 Alphabetical index 28 @ISO1997 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced orutilized in anyform orbyanymeans,electronicormechanical,includingphotocopying and microfilm, without permission in writing from the publisher. InternationalOrganizationforStandardization Case postale 56 . CH-1211 Geneve 20 . Switzerland Internet [email protected] X.400 C=ch; a=400net; p=iso; 0=isocs; s=central Printed in Switzerland - ernational Organization for Standardizatior No reproduction or netwvorking permited withoutlicense from IHS Not for Resale @ISO IS012491:1997(E) Foreword ISO(theInternationalOrganization for Standardization)isaworldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through isO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non- governmental, in liaison with isO, also take part in the work. Iso collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft international Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard ISO 12491 was prepared by Technical Committee ISO/TC 98, Bases for design of structures, Subcommittee SC 2, Reliability of structures. Annex A of this International Standard is for information only. ili No reproduction or networking permitted without license from IHS Not for Resale