1、BSI Standards Publication BS ISO 7870-5:2014 Control charts Part 5: Specialized control chartsBS ISO 7870-5:2014 BRITISH STANDARD National foreword This British Standard is the UK implementation of ISO 7870-5:2014. The UK participation in its preparation was entrusted to Technical Committee SS/4, St
2、atistical Process Management. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Instituti
3、on 2014. Published by BSI Standards Limited 2014 ISBN 978 0 580 68961 1 ICS 03.120.30 Compliance with a British Standard cannot confer immunity from legal obligations. This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 January 2014. Amendment
4、s issued since publication Date Text affectedBS ISO 7870-5:2014 ISO 2014 Control charts Part 5: Specialized control charts Cartes de contrle Partie 5: Cartes de contrle particulires INTERNATIONAL STANDARD ISO 7870-5 First edition 2014-01-15 Reference number ISO 7870-5:2014(E)BS ISO 7870-5:2014ISO 78
5、70-5:2014(E)ii ISO 2014 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2014 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 inte
6、rnet or an intranet, without prior written permission. Permission can be requested 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
7、 www.iso.org Published in SwitzerlandBS ISO 7870-5:2014ISO 7870-5:2014(E) ISO 2014 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 T erms and definitions . 1 4 Symbols and abbreviated terms . 4 4.1 Symbols . 4 4.2 Abbreviated terms . 5 5 Specia
8、lized control charts . 5 6 Moving average and moving range control charts . 5 6.1 Control limits 6 6.2 Interpretation 6 6.3 Advantages . 6 6.4 Limitations 6 6.5 Example . 6 7 z- chart. 9 7.1 Control limits 9 7.2 Advantages 10 7.3 Limitations .10 7.4 Example 10 8 Group control chart 10 8.1 Control li
9、mits .12 8.2 Advantages 12 8.3 Limitations .13 8.4 Example 13 9 High-low control chart .16 9.1 Control limits .16 9.2 Interpretation .17 9.3 Advantages 17 9.4 Limitations .17 9.5 Example 17 10 Trend control chart .19 10.1 Control limits .20 10.2 Advantages 20 10.3 Limitations .21 10.4 Example 21 11
10、C ontr ol chart for c oefficient of v ariation .24 11.1 Control limits .24 11.2 Advantage .24 11.3 Limitation .24 11.4 Example 25 12 Control chart for non-normal data .26 12.1 Control limits .27 12.2 Example 28 13 Standardized p- chart .32 13.1 Control limits .34 13.2 Advantages and limitations .34
11、13.3 Example 34BS ISO 7870-5:2014ISO 7870-5:2014(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Ea
12、ch 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 Internatio
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14、t types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall n
15、ot be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents). Any trade name used in this document is i
16、nformation given for the convenience of users and does not constitute an endorsement. For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) s
17、ee the following URL: Foreword - Supplementary information The committee responsible for this document is ISO/TC 69, Applications of statistical methods, Subcommittee SC 4, Applications of statistical methods in process management. ISO 7870 consists of the following parts, under the general title Co
18、ntrol charts: Part 1: General guidelines Part 2: Shewhart control charts Part 3: Acceptance control charts Part 4: Cumulative sum control charts Part 5: Specialized control charts Part 6: EWMA control chartsiv ISO 2014 All rights reservedBS ISO 7870-5:2014ISO 7870-5:2014(E) Introduction The Shewhart
19、 control charts as given in ISO 7870-2 aid in detection of unnatural patterns of variations in data from repetitive processes and provide criteria for detecting a lack of statistical control. However, there may be several special situations for variables data where Shewhart control charts may be ina
20、dequate, insufficient or less efficient in detecting the unnatural patterns of variation of the process, particularly where: a) it takes considerable time to produce an item and as such sample results are available at large intervals; b) there are several subgroup sources that have approximately the
21、 same production rate, process average and process capability; c) process average is changing systematically; d) sample size is large and sequence of production is irrelevant; e) process does not have a constant target value. In such situations, specialized control charts are to be used. Similarly,
22、special situations may be encountered in dealing with attributes data. There may be situations when criticality of an incidence in a subgroup (nonconformity) is a matter of concern, but different nonconformities are having different criticality. As such, all types of nonconformities cannot be treate
23、d alike. Depending upon criticality, different ratings (weights) are required to be given to each class of nonconformity, and accordingly demerit scores are calculated. The control limits are calculated based on such demerit scores and accordingly control charts are plotted to exercise process contr
24、ol. There may be situations when inspection by attributes is preferred to that by variables, from practical considerations, for controlling both the location and the variability parameters of a measureable characteristic of a process (for example, inspection by gauging). The information is also avai
25、lable on the number of items less than the lower specification limits (no-go gauge) as well as the number of items above upper specification limit (go gauge) in assembly operations. In such situation, a specialized pair of control charts may be used. There may also be situations when data do not fol
26、low normal distribution. Such situations of non-normal data are quite often encountered in service industry, besides in special processes of manufacturing. In such a situation specialized control chart is to be used. This part of ISO 7870 has been prepared to provide guidance on the use of specializ
27、ed control charts to address above typical, unusual situations. ISO 2014 All rights reserved vBS ISO 7870-5:2014BS ISO 7870-5:2014Control charts Part 5: Specialized control charts 1 Scope This part of ISO 7870 establishes a guide to the use and understanding of specialized control charts in situatio
28、ns where commonly used Shewhart control chart approach to the methods of statistical control of a process may either be not applicable or less efficient in detecting unnatural patterns of variation of the process. The specialized control charts included in this part of ISO 7870 for variables data ar
29、e: a) moving average and moving range charts; b) z-charts; c) group control charts; d) highlow control charts; e) trend control charts; f) control charts for coefficient of variation; g) control charts for non-normal data. For attributes data, specialized control charts included in this part of ISO
30、7870 are: a) standardized p-charts; b) demerit control charts; c) control charts for inspection by gauging. This part of ISO 7870 also provides guidance as to when each of the above control charts should be used, their control limits, advantages and limitations. Each control chart is illustrated wit
31、h an example. 2 Normative references The following referenced documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced docu
32、ment (including any amendments) applies. ISO 3534-2, Statistics Vocabulary and symbols Part 2: Applied statistics 3 T erms a nd definiti ons For the purposes of this document, the terms and definitions given in ISO 3534-2 and the following apply. INTERNATIONAL ST ANDARD ISO 7870-5:2014(E) ISO 2014 A
33、ll rights reserved 1BS ISO 7870-5:2014ISO 7870-5:2014(E) 3.1 control chart chart on which some statistical measure of a series of samples is plotted in a particular order to steer the process with respect to that measure and to control and reduce variation Note 1 to entry: The particular order is us
34、ually based on time or sample number order. Note 2 to entry: The control chart operates most effectively when the measure is a process variable which is correlated with an ultimate product or service characteristic. SOURCE: ISO 3534-2:2006, 2.3.1 3.2 Shewhart control chart control chart with Shewhar
35、t control limits intended primarily to distinguish between the variation in the plotted measure due to random causes and that due to special causes SOURCE: ISO 3534-2:2006, 2.3.2 3.3 variables control chart Shewhart control chart in which the measure plotted represents data on a continuous scale SOU
36、RCE: ISO 3534-2:2006, 2.3.6 3.4 attributes control chart Shewhart control chart in which the measure plotted represents countable or categorized data SOURCE: ISO 3534-2:2006, 2.3.7 3.5 Xbar control chart average control chart variables control chart for evaluating the process level in terms of subgr
37、oup averages SOURCE: ISO 3534-2:2006, 2.3.12 3.6 R chart range control chart variables control chart for evaluating variation in terms of subgroup ranges Note 1 to entry: The value of the subgroup range, given by the symbol R, is the difference between the largest and smallest observation of a subgr
38、oup. Note 2 to entry: The average of the range values for all subgroups is denoted by the symbol R . SOURCE: ISO 3534-2:2006, 2.3.18 3.7 moving average control chart control chart for evaluating the process level in terms of the arithmetic average of each successive n observations Note 1 to entry: T
39、his chart is particularly useful when only one observation per subgroup is available. Examples are process characteristics such as temperature, pressure and time. Note 2 to entry: The current observation replaces the oldest of the latest n + 1 observations. Note 3 to entry: It has the disadvantage o
40、f an unweighted carry-over effect lasting n points. SOURCE: ISO 3534-2:2006, 2.3.142 ISO 2014 All rights reservedBS ISO 7870-5:2014ISO 7870-5:2014(E) 3.8 moving range control chart variables control chart for evaluating variation in terms of the range of each successive n observations Note 1 to entr
41、y: The current observation replaces the oldest of the latest n +1 observations. SOURCE: ISO 3534-2:2006, 2.3.20 3.9 z-chart variables control chart for evaluating the process in terms of subgroup standardized normal variates 3.10 group control chart for averages variables control chart for evaluatin
42、g the process level in terms of subgroup (with several sources) highest and lowest averages with corresponding source identification 3.11 group control chart for ranges variables control chart for evaluating the process variation in terms of subgroup (with several sources) highest ranges with corres
43、ponding source identification 3.12 high low control chart variables control chart for evaluating the process level in terms of subgroup largest and smallest values 3.13 trend control chart control chart for evaluating the process level with respect to the deviation of the subgroup averages from an e
44、xpected change in the process level Note 1 to entry: The trend may be determined empirically or by regression techniques. Note 2 to entry: A trend is an upward or downward tendency, after exclusion of the random variation and cyclical effects, when observed values are plotted in the time order of th
45、e observations. SOURCE: ISO 3534-2:2006, 2.3.17 3.14 c o n t r o l c h a r t f o r c o e f f i c i e n t o f v a r i a t i o n variables control chart for evaluating variation in terms of subgroup coefficient of variation 3.15 p chart proportion or percent categorized units control chart attributes
46、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 to entry: In the quality field, the classification usually takes the form of “nonconforming unit”. Note 2 to entry: The “p” chart is applied particul
47、arly when the sample size is variable. Note 3 to entry: The plotted measure can be expressed as a proportion or as a percentage. SOURCE: ISO 3534-2:2006, 2.3.11 3.16 standardized p-chart attributes control chart where proportions of given classification are expressed as standardized normal variates
48、Note 1 to entry: In this chart, the centre line is zero, upper control limit is +3 and lower control limit is 3. ISO 2014 All rights reserved 3BS ISO 7870-5:2014ISO 7870-5:2014(E) 3.17 demerit control chart quality score chart multiple characteristic control chart for evaluating the process level wh
49、ere different weights are apportioned to events depending on their perceived significance SOURCE: ISO 3534-2:2006, 2.3.23 3.18 control chart for inspection by gauging attributes control chart when the inspection is done by gauging and the information is available on the number of units above upper gauge limit and below lower gauge limit 4 Symbols and abbreviated terms 4.1 Symbols n subgroup sample size k number of subgroups x individual measured value average value of i-th subgroup x average of the subgr
