1、BSI Standards Publication BS ISO 7870-1:2014 Control charts Part 1: General guidelinesBS ISO 7870-1:2014 BRITISH STANDARD National foreword This British Standard is the UK implementation of ISO 7870-1:2014. It supersedes BS ISO 7870-1:2007 which is withdrawn. The UK participation in its preparation
2、was entrusted to Technical Committee SS/4, Statistical 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
3、 application. The British Standards Institution 2014. Published by BSI Standards Limited 2014 ISBN 978 0 580 82464 7 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 Str
4、ategy Committee on 28 February 2014. Amendments issued since publication Date Text affectedBS ISO 7870-1:2014 ISO 2014 Control charts Part 1: General guidelines Cartes de contrle Partie 1: Lignes directrices gnrales INTERNATIONAL STANDARD ISO 7870-1 Second edition 2014-02-01 Reference number ISO 787
5、0-1:2014(E)BS ISO 7870-1:2014ISO 7870-1:2014(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 p
6、hotocopying, or posting on the internet 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 74
7、9 09 47 E-mail copyrightiso.org Web www.iso.org Published in SwitzerlandBS ISO 7870-1:2014ISO 7870-1:2014(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 7 5 Concepts 7 5.1 Control chart . 7 5.2
8、Statistical control of a process . 8 5.3 Acceptance of a process 8 5.4 Management of a process with a natural drift . 8 5.5 Risks of decision errors . 8 5.6 Design of data collection . 9 5.7 Control charts for variables and attributes data .11 6 Types of control charts11 7 Charts for process stabili
9、ty .12 7.1 General 12 7.2 Partial listing of Shewhart and related control charts .12 8 Charts for process acceptance .14 8.1 General 14 8.2 Acceptance control charts (see ISO 7870-3) 15 8.3 Modified control charts (control charts with modified limits; see ISO 7870-3) .15 9 Process adjustment 15 Bibl
10、iography .16BS ISO 7870-1:2014ISO 7870-1:2014(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. Each
11、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
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13、ypes 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 not
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15、rmation 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) see
16、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. This second edition of ISO 7870-1 cancels and replaces the first editio
17、n (ISO 7870-1:2007), which has been technically revised. ISO 7870 consists of the following parts, under the general title Control charts: Part 1: General guidelines Part 2: Shewhart control charts Part 3: Acceptance control charts Part 4: Cumulative sum charts Part 5: Specialized control charts Par
18、t 6: EWMA control chartsiv ISO 2014 All rights reservedBS ISO 7870-1:2014ISO 7870-1:2014(E) Introduction Every production, service, or administrative process contains a certain amount of variability due to the presence of a large number of causes. The observed results from a process are, as a result
19、, 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 method that can be used to a) indicate if the process
20、 is 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) compare information from samples representing the current stat
21、e of a process against control limits reflecting this variability, with the objective of determining whether the process variability has remained stable or is reduced or increased, d) identify, investigate, and possibly reduce/eliminate the effect of special causes of variability, which can drive th
22、e 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, etc., f) determine if the process is behaving in a predictable and stable manner so that it will be possible to assess if the p
23、rocess 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 process adjustment through prediction using statistical models, and i) ass
24、ist 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 online indicator about the behaviour of the process. However, in ord
25、er for the control chart to be a reliable and efficient indicator of the state of the process, careful attention has to be paid at the planning stage to such matters as selecting the appropriate type of chart for the process under study and determining a proper sampling scheme. General concepts usef
26、ul to a successful design of a control chart are presented in this part of ISO 7870. ISO 2014 All rights reserved vBS ISO 7870-1:2014BS ISO 7870-1:2014Control charts Part 1: General guidelines 1 Scope This part of ISO 7870 presents key elements and philosophy of the control chart approach, and ident
27、ifies a wide variety of control charts (including those related to the Shewhart control chart, those stressing process acceptance or online process adjustment, and specialized control charts). It presents an overview of the basic principles and concepts and illustrates the relationship among various
28、 control chart approaches 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 documents, in whole or i
29、n 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 document (including any amendments) applies. ISO 3534-2, Statistics Vocabulary and symbols
30、 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. 3.1 control chart chart with control limits (3.2) on which some statistical measure of a series of samples is plotted in a particular order
31、 to steer the process with respect to that measure Note 1 to entry: The particular order is usually 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 charac
32、teristic. SOURCE: ISO 3534-2:2006, 2.3.1 3.2 control limit statistical value defining an intended level of stability for a produced characteristic Note 1 to entry: One or two control limits are represented on the control chart. Note 2 to entry: The term “stability” is not meant only for a process in
33、 control but it can also be stability against a target value. INTERNATIONAL ST ANDARD ISO 7870-1:2014(E) ISO 2014 All rights reserved 1BS ISO 7870-1:2014ISO 7870-1:2014(E) 3.3 Shewhart control chart control chart (3.1) with Shewhart control limits (3.4) intended primarily to distinguish between the
34、variation in the plotted measure due to random causes and that due to special causes SOURCE: ISO 3534-2:2006, 2.3.2 3.4 Shewhart control limit control limit (3.2) determined statistically from the variation of the process due to the random causes alone 3.5 acceptance control chart control chart (3.1
35、) intended primarily to evaluate whether or not the plotted measure can be expected to satisfy specified tolerances SOURCE: ISO 3534-2:2006, 2.3.3 3.6 process adjustment control chart control chart (3.1) which uses a prediction model of the process to estimate and plot the future course of the proce
36、ss if no change is made, and to quantify the change to be made to keep the process deviations within acceptable limits SOURCE: ISO 3534-2:2006, 2.3.4 3.7 variables control chart control chart (3.1) in which the plotted measure represents data on a continuous scale SOURCE: ISO 3534-2:2006, 2.3.6 3.8
37、attributes control chart control chart (3.1) in which the plotted measure represents countable or categorized data SOURCE: ISO 3534-2:2006, 2.3.7 3.9 c chart count control chart attributes control chart (3.8) for the number of incidences where the opportunity for occurrence is fixed Note 1 to entry:
38、 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 nonconformities and the fixed opportunity relates to samples of constant size or fixed amount of material. Examples are “flaws in each
39、 100 m 2of fabric” and “errors in each 100 invoices”. SOURCE: ISO 3534-2:2006, 2.3.8 3.10 u chart count per unit control chart attributes control chart (3.8) for the number of incidences per unit where the opportunity is variable Note 1 to entry: Incidences of a particular type, for example, number
40、of absentees and number of sales leads, form the count. In the quality field, incidences are often expressed as nonconformities and the variable opportunity relates to subgroups of variable size or variable amounts of material. SOURCE: ISO 3534-2:2006, 2.3.92 ISO 2014 All rights reservedBS ISO 7870-
41、1:2014ISO 7870-1:2014(E) 3.11 np chart number of categorized units control chart attributes control chart (3.8) for number of units of a given classification where the subgroup size is constant Note 1 to entry: In the quality field, the classification usually takes the form of “nonconforming units”.
42、 SOURCE: ISO 3534-2:2006, 2.3.10 3.12 p chart proportion categorized units control chart percent categorized units control chart attributes control chart (3.8) 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
43、entry: In the quality field, the classification usually takes the form of “nonconforming unit”. Note 2 to entry: The p chart is applied particularly when the subgroup 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,
44、2.3.11 3.13 standardized p chart attributes control chart (3.8)where proportion of given classification are expressed as standardized normal variates 3.14 X bar control chart average control chart variables control chart (3.7) for evaluating the process level in terms of subgroup averages SOURCE: IS
45、O 3534-2:2006, 2.3.12 3.15 median control chart variables control chart (3.7) for evaluating the process level in terms of subgroup medians SOURCE: ISO 3534-2:2006, 2.3.13 3.16 moving average control chart control chart (3.1) for evaluating the process level in terms of the arithmetic average of eac
46、h successive n observations Note 1 to entry: This 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 observati
47、ons. Note 3 to entry: It has the disadvantage of an unweighted carry-over effect lasting n points. SOURCE: ISO 3534-2:2006, 2.3.14 ISO 2014 All rights reserved 3BS ISO 7870-1:2014ISO 7870-1:2014(E) 3.17 individuals control chart X control chart variables control chart (3.7) for evaluating the proces
48、s level in terms of the individual observations in the sample Note 1 to entry: This chart is usually accompanied by a moving range chart, frequently with n = 2. Note 2 to entry: It sacrifices the advantages of averaging in terms of minimizing random variation and the normal distribution central limi
49、t theorem assumptions. Note 3 to entry: Individual values are expressed by the symbols x 1 , x 2 , x 3 , Note 4 to entry: In the case of charts for individuals, the symbol R represents the value of the moving range, which is the absolute value of the difference between two successive values, thus, xxxx , etc. SOURCE: ISO 3534-2:2006, 2.3.15, modified 3.18 cumulative sum control chart CUSUM chart control chart (3.1) where the cumulative sum of deviations of successive sample values from a referen
