1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA
2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any
3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. ISBN 978-0-626-21180-6 SANS 7870-1:2008 Edition 1 ISO 7870-1:2007 Edition 1SOUTH AFRICAN NATIONAL STANDARD Control charts Part 1: General guidelines This
4、 national standard is the identical implementation of ISO 7870-1:2007 and is adopted with the permission of the International Organization for Standardization. Published by Standards South Africa 1 dr lategan road groenkloof private bag x191 pretoria 0001 tel: 012 428 7911 fax: 012 344 1568 internat
5、ional code + 27 12 www.stansa.co.za Standards South Africa This standard may only be used and printed by approved subscription and freemailing clients of the SABS.SANS 7870-1:2008 Edition 1 ISO 7870-1:2007 Edition 1 Table of changes Change No. Date Scope National foreword This South African standard
6、 was approved by National Committee StanSA TC 169, Applications of statistical methods, in accordance with procedures of Standards South Africa, in compliance with annex 3 of the WTO/TBT agreement. This SANS document was published in April 2008. This standard may only be used and printed by approved
7、 subscription and freemailing clients of the SABS. Reference number ISO 7870-1:2007(E) ISO 2007INTERNATIONAL STANDARD ISO 7870-1 First edition 2007-10-01 Control charts Part 1: General guidelines Cartes de contrle Partie 1: Lignes directrices gnrales SANS 7870-1:2008This standard may only be used an
8、d printed by approved subscription and freemailing clients of the SABS.ISO 7870-1:2007(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are li
9、censed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobes licensing policy. The ISO Central Secretariat accepts no liability in this area. Adobe is a trademark of Adobe Systems Incorporated. Details of
10、 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 relatin
11、g to it is found, please inform the Central Secretariat at the address given below. COPYRIGHT PROTECTED DOCUMENT ISO 2007 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 photoc
12、opying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switz
13、erland ii ISO 2007 All rights reservedSANS 7870-1:2008This standard may only be used and printed by approved subscription and freemailing clients of the SABS.ISO 7870-1:2007(E) ISO 2007 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references . 1 3 Terms an
14、d definitions. 1 4 Symbols . 6 5 Concepts 6 5.1 Control chart . 6 5.2 Statistical control of a process . 7 5.3 Acceptance of a process . 7 5.4 Management of a process with a natural drift . 8 5.5 Risks of decision errors. 8 5.6 Design of data collection . 8 5.7 Control charts for variables and attri
15、butes data . 9 6 Types of control charts 10 7 Charts for process stability . 10 7.1 General. 10 7.2 Partial listing of Shewhart and related control charts 11 8 Charts for process acceptance . 13 8.1 General. 13 8.2 Acceptance control charts. 13 8.3 Modified control charts (control charts with modifi
16、ed limits) 13 9 Process adjustment 13 Bibliography . 15 SANS 7870-1:2008This standard may only be used and printed by approved subscription and freemailing clients of the SABS.ISO 7870-1:2007(E) iv ISO 2007 All rights reservedForeword ISO (the International Organization for Standardization) is a wor
17、ldwide 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
18、 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. International Standards are drafted
19、in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standar
20、d requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 7870-1 was prepared by
21、Technical Committee ISO/TC 69, Applications of statistical methods, Subcommittee SC 4, Applications of statistical methods in process management. This first edition of ISO 7870-1 cancels and replaces ISO 7870:1993. ISO 7870 consists of the following parts, under the general title Control charts: Par
22、t 1: General guidelines The following parts are planned: Part 2: Shewhart control charts Part 3: Process acceptance control charts Part 4: Process adjustment control charts Part 5: Specialized control charts Part 6: Guide to the application of statistical control charts SANS 7870-1:2008This standard
23、 may only be used and printed by approved subscription and freemailing clients of the SABS.ISO 7870-1:2007(E) ISO 2007 All rights reserved v Introduction Every production, service, or administrative process contains a certain amount of variability due to the presence of a large number of causes. The
24、 observed results from a process are, as a result, not constant. Studying this variability to gain an understanding of its characteristics provides a basis for taking action on a process. Control charts are a fundamental tool of statistical process control (SPC). They provide a simple graphical meth
25、od that can be used to: a) indicate if the process is, or is not, stable, i.e. operating within a stable system of random causes, also known as inherent variability and referred to as being in a “state of statistical control”; b) estimate the magnitude of the inherent variability of the process; c)
26、compare information from samples representing the current state of a process against limits reflecting this variability, with the objective of determining whether the process has remained stable or not and variability has been reduced or not; d) identify, investigate and possibly reduce/eliminate th
27、e effect of special causes of variability, which may drive the process to an unacceptable level of performance; e) aid in the regulation of a process through the identification of patterns of variability such as trends, runs, cycles and the like; f) determine if the process is behaving in a predicta
28、ble and stable manner so that it will be possible to assess if the process is able to meet specifications; g) determine whether or not the process can be expected to satisfy product or service requirements and process capability for the characteristic(s) being measured; h) provide a basis for proces
29、s adjustment through prediction using statistical models; i) assist in the assessment of the performance of a measurement system. A major virtue of the control chart is its ease of construction and use. It provides the production or service operator, engineer, administrator and manager with an on-li
30、ne indicator about the behaviour of the process. However, in order for the control chart to be a reliable and efficient indicator of the state of the process, careful attention must be paid at the planning stage to such matters as selecting the appropriate type of chart for the process under study a
31、nd determining a proper sampling scheme. General concepts useful to a successful design of a control chart are presented in this part of ISO 7870. SANS 7870-1:2008This standard may only be used and printed by approved subscription and freemailing clients of the SABS.SANS 7870-1:2008This standard may
32、 only be used and printed by approved subscription and freemailing clients of the SABS.INTERNATIONAL STANDARD ISO 7870-1:2007(E) ISO 2007 All rights reserved 1 Control charts Part 1: General guidelines 1 Scope This part of ISO 7870 presents key elements and philosophy of the control chart approach,
33、and identifies a wide variety of control charts (including those related to the Shewhart control chart and those stressing process acceptance or on-line process adjustment). It presents an overview of the basic principles and concepts and illustrates the relationship among various control chart appr
34、oaches to aid in the selection of the most appropriate standard for given circumstances. It does not specify statistical control methods using control charts. These methods will be specified in future parts of ISO 7870. 2 Normative references The following referenced documents are indispensable for
35、the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 3534-2:2006, Statistics Vocabulary and symbols Part 2: Applied statistics 3 Terms and definitions For
36、the purposes of this document, the terms and definitions given in ISO 3534-2 and the following apply. In some cases, additional clarification on terms from ISO 3534-2 is provided. 3.1 control chart chart on which some statistical measure of a series of samples is plotted in a particular order to ste
37、er the process with respect to that measure and to control and reduce variation NOTE 1 The particular order is usually based on time or sample number order. NOTE 2 The control chart operates most effectively when the measure is a process variable which is correlated with an ultimate product or servi
38、ce characteristic. ISO 3534-2:2006, 2.3.1 3.2 Shewhart control chart control chart with Shewhart control limits intended primarily to distinguish between the variation in the plotted measure due to random causes and that due to special causes ISO 3534-2:2006, 2.3.2 SANS 7870-1:2008This standard may
39、only be used and printed by approved subscription and freemailing clients of the SABS.ISO 7870-1:2007(E) 2 ISO 2007 All rights reserved3.3 acceptance control chart control chart intended primarily to evaluate whether or not the plotted measure can be expected to satisfy specified tolerances ISO 3534
40、-2:2006, 2.3.3 3.4 process adjustment control chart control chart which uses a prediction model of the process to estimate and plot the future course of the process if no change is made, and to quantify the change to be made to keep the process deviations within acceptable limits ISO 3534-2:2006, 2.
41、3.3 3.5 cumulative sum control chart CUSUM chart control chart where the cumulative sum of deviations of successive sample values from a reference value is plotted to detect shifts in the level of the measure plotted NOTE 1 The ordinate of each plotted point represents the algebraic sum of the previ
42、ous ordinate and the most recent deviation from the reference, target or control value. NOTE 2 The best discrimination of changes in level is achieved when reference value is equal to the overall average value. NOTE 3 The chart can be used in control, diagnostic or predictive mode. NOTE 4 When used
43、in control mode it can be interpreted graphically by a mask (e.g. V-mask) superimposed on the graph. A signal occurs if the path of the CUSUM intersects or touches the boundary of the mask. ISO 3534-2:2006, 2.3.5 3.6 variables control chart Shewhart control chart in which the measure plotted represe
44、nts data on a continuous scale ISO 3534-2:2006, 2.3.6 3.7 attribute control chart Shewhart control chart in which the measure plotted represents countable or categorized data ISO 3534-2:2006, 2.3.7 3.8 c chart count control chart attribute control chart for the number of incidences where the opportu
45、nity for occurrence is fixed NOTE Incidences of a particular type, for example, number of absentees, number of sales leads, form the count. In the quality field, incidences are often expressed as nonconformities and the fixed opportunity relates to samples of constant size or fixed amount of materia
46、l. Examples are “flaws in each 100 square metres of fabric” and “errors in each 100 invoices”. ISO 3534-2:2006, 2.3.8 SANS 7870-1:2008This standard may only be used and printed by approved subscription and freemailing clients of the SABS.ISO 7870-1:2007(E) ISO 2007 All rights reserved 3 3.9 u chart
47、count per unit control chart attribute control chart for the number of incidences per unit where the opportunity is variable NOTE Incidences of a particular type, for example, number of absentees and number of sales leads, form the count. In the quality field, incidences are often expressed as nonco
48、nformities and the variable opportunity relates to subgroups of variable size or variable amounts of material. ISO 3534-2:2006, 2.3.9 3.10 np chart number of categorized units control chart attribute control chart for number of units of a given classification where the sample size is constant NOTE I
49、n the quality field, the classification usually takes the form of “nonconforming units”. ISO 3534-2:2006, 2.3.10 3.11 p chart proportion or percent categorized units control chart attribute control chart for number of units of a given classification per total number of units in the sample expressed either as a proportion or percent NOTE 1 In the quality field, the classification usually takes the form of “nonconforming unit”. NOTE 2 The “p” chart is applied particularly when the sample size is variable. NOTE
