BS ISO 7870-1-2014 Control charts General guidelines《控制图表 一般指南》.pdf

1、BSI Standards PublicationBS ISO 7870-1:2014Control chartsPart 1: General guidelinesBS ISO 7870-1:2014 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 7870-1:2014. Itsupersedes BS ISO 7870-1:2007 which is withdrawn.The UK participation in its preparation was ent

2、rusted to TechnicalCommittee SS/4, Statistical Process Management.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication.

3、 The British Standards Institution 2014. Published by BSI StandardsLimited 2014ISBN 978 0 580 82464 7ICS 03.120.30Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 2

4、8 February 2014.Amendments issued since publicationDate Text affectedBS ISO 7870-1:2014 ISO 2014Control charts Part 1: General guidelinesCartes de contrle Partie 1: Lignes directrices gnralesINTERNATIONAL STANDARDISO7870-1Second edition2014-02-01Reference numberISO 7870-1:2014(E)BS ISO 7870-1:2014IS

5、O 7870-1:2014(E)ii ISO 2014 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2014All 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 in

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7、.iso.orgPublished in SwitzerlandBS ISO 7870-1:2014ISO 7870-1:2014(E) ISO 2014 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Symbols 75 Concepts 75.1 Control chart . 75.2 Statistical control of a process . 85.3 Acceptance

8、of a process 85.4 Management of a process with a natural drift . 85.5 Risks of decision errors . 85.6 Design of data collection . 95.7 Control charts for variables and attributes data .116 Types of control charts117 Charts for process stability .127.1 General 127.2 Partial listing of Shewhart and re

9、lated control charts .128 Charts for process acceptance .148.1 General 148.2 Acceptance control charts (see ISO 7870-3) 158.3 Modified control charts (control charts with modified limits; see ISO 7870-3) .159 Process adjustment 15Bibliography .16BS ISO 7870-1:2014ISO 7870-1:2014(E)ForewordISO (the I

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14、etails 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 information given for the convenience of users and does not constitute a

15、n 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 the following URL: Foreword - Supplementary informationThe committee

16、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 edition (ISO 7870-1:2007), which has been technically revised.ISO 7870 consis

17、ts 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 Part 6: EWMA control chartsiv ISO 2014 All rights reservedBS ISO 7870-1:201

18、4ISO 7870-1:2014(E)IntroductionEvery 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, not constant. Studying this variability to gain an understanding of its

19、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 toa) indicate if the process is stable, i.e. operating within a stable system of random causes, also kno

20、wn 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 state of a process against control limits reflecting this variability, with the ob

21、jective 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 the process to an unacceptable level of performance,e) aid in the regulation of a

22、 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 process is able to meet specifications,g) determine whether or not the process can

23、 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, andi) assist in the assessment of the performance of a measurement system.A major virtue of t

24、he 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 order for the control chart to be a reliable and efficient indicator of the state of the

25、 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 useful to a successful design of a control chart are presented in this part of ISO 7870. I

26、SO 2014 All rights reserved vBS ISO 7870-1:2014BS ISO 7870-1:2014Control charts Part 1: General guidelines1 ScopeThis part of ISO 7870 presents key elements and philosophy of the control chart approach, and identifies a wide variety of control charts (including those related to the Shewhart control

27、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 control chart approaches to aid in the selection of the most appropriate standard for gi

28、ven circumstances. It does not specify statistical control methods using control charts. These methods will be specified in future parts of ISO 7870.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its applicati

29、on. 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 Part 2: Applied statistics3 Terms and definitionsFor the purposes of this document, the ter

30、ms and definitions given in ISO 3534-2 and the following apply.3.1control chartchart with control limits (3.2) on which some statistical measure of a series of samples is plotted in a particular order to steer the process with respect to that measureNote 1 to entry: The particular order is usually b

31、ased 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, 2.3.13.2control limitstatistical value defining an intended level of

32、 stability for a produced characteristicNote 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 control but it can also be stability against a target value.INTERNATIONAL STANDARD ISO 7870-1:2014(E) ISO 2

33、014 All rights reserved 1BS ISO 7870-1:2014ISO 7870-1:2014(E)3.3Shewhart control chartcontrol chart (3.1) with Shewhart control limits (3.4) intended primarily to distinguish between the variation in the plotted measure due to random causes and that due to special causesSOURCE: ISO 3534-2:2006, 2.3.

34、23.4Shewhart control limitcontrol limit (3.2) determined statistically from the variation of the process due to the random causes alone3.5acceptance control chartcontrol chart (3.1) intended primarily to evaluate whether or not the plotted measure can be expected to satisfy specified tolerancesSOURC

35、E: ISO 3534-2:2006, 2.3.33.6process adjustment control chartcontrol chart (3.1) 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 limitsSOURCE

36、: ISO 3534-2:2006, 2.3.43.7variables control chartcontrol chart (3.1) in which the plotted measure represents data on a continuous scaleSOURCE: ISO 3534-2:2006, 2.3.63.8attributes control chartcontrol chart (3.1) in which the plotted measure represents countable or categorized dataSOURCE: ISO 3534-2

37、:2006, 2.3.73.9c chartcount control chartattributes control chart (3.8) for the number of incidences where the opportunity for occurrence is fixedNote 1 to entry: Incidences of a particular type, for example, number of absentees and number of sales leads, form the count. In the quality field, incide

38、nces 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 100 m2of fabric” and “errors in each 100 invoices”.SOURCE: ISO 3534-2:2006, 2.3.83.10u chartcount per unit control chartattributes contro

39、l chart (3.8) for the number of incidences per unit where the opportunity is variableNote 1 to entry: 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 variable

40、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 7870-1:2014ISO 7870-1:2014(E)3.11np chartnumber of categorized units control chartattributes control chart (3.8) for number of units of a given classif

41、ication where the subgroup size is constantNote 1 to entry: In the quality field, the classification usually takes the form of “nonconforming units”.SOURCE: ISO 3534-2:2006, 2.3.103.12p chartproportion categorized units control chartpercent categorized units control chartattributes control chart (3.

42、8) for number of units of a given classification per total number of units in the sample expressed either as a proportion or percentNote 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 particularly when the s

43、ubgroup 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, 2.3.113.13standardized p chartattributes control chart (3.8)where proportion of given classification are expressed as standardized normal variates3.14X bar contr

44、ol chartaverage control chartvariables control chart (3.7) for evaluating the process level in terms of subgroup averagesSOURCE: ISO 3534-2:2006, 2.3.123.15median control chartvariables control chart (3.7) for evaluating the process level in terms of subgroup mediansSOURCE: ISO 3534-2:2006, 2.3.133.

45、16moving average control chartcontrol chart (3.1) for evaluating the process level in terms of the arithmetic average of each successive n observationsNote 1 to entry: This chart is particularly useful when only one observation per subgroup is available. Examples are process characteristics such as

46、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 of an unweighted carry-over effect lasting n points.SOURCE: ISO 3534-2:2006, 2.3.14 ISO 2014 All rights reserved 3BS ISO 7870-1:2014I

47、SO 7870-1:2014(E)3.17individuals control chartX control chartvariables control chart (3.7) for evaluating the process level in terms of the individual observations in the sampleNote 1 to entry: This chart is usually accompanied by a moving range chart, frequently with n = 2.Note 2 to entry: It sacri

48、fices the advantages of averaging in terms of minimizing random variation and the normal distribution central limit theorem assumptions.Note 3 to entry: Individual values are expressed by the symbols x1, x2, x3,Note 4 to entry: In the case of charts for individuals, the symbol R represents the value

49、 of the moving range, which is the absolute value of the difference between two successive values, thus, xxxx1223, , etc.SOURCE: ISO 3534-2:2006, 2.3.15, modified3.18cumulative sum control chartCUSUM chartcontrol chart (3.1) 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 plottedNote 1 to entry: The ordinate of each plotted point represents the algebraic sum of the previous ordinate and the most recent deviation from th