ISO INTERNATIONAL STANDARD 7870-6 First edition 2016-02-15 Control charts Part 6: EWMA control charts Cartes de controle - Partie 6: Cartes de controle de EWMA Reference number IS0 7870-6:2016(E) ISO InternationalOrganization for Standardization =ZHEJIANG INST OF STANDARDIZATION C1 5956617 @ISO2016 Notfor Resale,2016/4/2602:05:21 No reproduction or networking permitted without license from IHS IS0 7870-6:2016(E) COPYRIGHTPROTECTEDDOCUMENT IS0 2016, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISO's member body in the country of the requester. ISOcopyrightoffice Ch. de Blandonnet 8 . CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 copyright@iso.org www.iso.org Intenatinair PrganizationforStandardization nsee-ZHEJIANG INSTOF STANDARDIZAoSQ6- All rights reserved Not for Resale, 2016/4/26 02:05:21 etworking permitted without license from IHS IS0 7870-6:2016(E) Contents Page Foreword ..iv Introduction ..V 1 Scope. ..1 2 Normative references 3 Symbols and abbreviated terms 4 EWMA for inspection by variables .2 4.1 General .2 4.2 Weighted average explained. .3 4.3 Control limits for EWMA control chart 4 4.4 Construction of EWMA control chart .4 4.5 Example. .6 5 Choice of the control chart .9 5.1 Shewhart control chart versus EWMA control chart .9 5.2 Average run length 10 5.3 Choice of parametersfor EWMA control chart .10 5.3.1 Choice of .10 5.3.2 Choice of L2 .11 5.3.3 Calculation for n 5.3.4 Example .12 6 Procedure for implementing the EWMA control chart ..12 7 Sensitivity of the EWMA to non-normality ..13 8 Advantages and limitations ..13 8.1 Advantages ..13 8.2 Limitations ..13 Annex A (informative) Application of the EWMA control chart .14 Annex B (normative) EWMA control chart for controlling a proportion of nonconforming units...18 Annex C (normative) EWMA control charts for a number of nonconformities. .20 Annex D (informative) Control chart effectiveness ..22 Bibliography .26 iii lout license from IHS