1、BS 5702-2:2008Guide to statistical process control (SPC) charts for variables Part 2: Charts for individual valuesICS 03.120.30NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDPublishing and copyright informationThe BSI copyright notice displayed in this document
2、 indicates when the document was last issued. BSI 2008ISBN 978 0 580 53005 0The following BSI references relate to the work on this standard:Committee reference SS/4Draft for comment 05/30126058 DCPublication historyFirst published April 2008Amendments issued since publicationAmd. no. Date Text affe
3、ctedBS 5702-2:2008 BSI 2008 iBS 5702-2:2008ContentsForeword iii1 Scope 12 Normative references 13 Terms, definitions and symbols 24 Role of control charts in process control and improvement 85 Classes of data and selection of appropriate chart 116 Control charts for individual measurements 127 Const
4、ruction and use of standard individual and moving range control charts 148 Construction and use of standard moving mean and moving range charts 259 Construction and use of median control charts 3010 Construction and use of basic cusum charts 3311 Construction and use of individual measurement cusum
5、charts for process control 3612 Construction and use of individual and moving range charts for attribute data 37AnnexesAnnex A (informative) Case studies for typical applications 45Annex B (informative) Control chart templates 55Annex C (normative) Relationship between Cpkand percentages and parts-p
6、er-million (ppm) out-of-specification 57Bibliography 58List of figuresFigure 1 Application sequence for process control, performance assessment and improvement 9Figure 2 Focus on influential process characteristics rather than product yield 10Figure 3 Road map for control charts 12Figure 4 Provision
7、al individual and moving range chart for silicon content in steel 19Figure 5 Provisional control chart for silicon content 21Figure 6 Provisional histogram of silicon content 22Figure 7 Performance capability analysis using provisional data 22Figure 8 Comparison of before and after results 24Figure
8、9 Histogram and capability analysis of data after adjustment of mean 24Figure 10 Spreadsheet-based moving mean and moving range control chart for silicon content 29Figure 11 Median control chart for spend versus budget 32Figure 12 Conventional individuals chart for spend versus budget 32Figure 13 Ba
9、sic cusum chart for % silicon content 34Figure 14 Refined individuals control chart for % silicon content 35Figure 15 Cusum chart for % silicon content in control mode 36Figure 16 Cusum chart for nonconforming deliveries 39Figure 17 np control chart for nonconforming deliveries 40Figure 18 X control
10、 chart for nonconforming deliveries 40Figure 19 Cusum chart for fabric nonconformities 41Figure 20 Cusum chart for fabric nonconformities per roll 42Figure 21 c chart for fabric nonconformities per roll 42BS 5702-2:2008ii BSI 2008Figure 22 c chart of outages per week 22Figure 23 Individuals chart of
11、 system outage rate per month 44Figure A.1 Individuals chart for strontium-90 in cows milk in UK location 47Figure A.2 Individuals chart for caesium-137 in cows milk 48Figure A.3 Individuals chart of daily fasting blood sugar levels 49Figure A.4 Individuals chart for peak expiratory flow rate 51Figu
12、re A.5 Cusum chart of the number of trades executed at the LSE per month 52Figure A.6 Individuals chart of the number of trades executed at the LSE per month 53Figure A.7 FTSE all share index by month 54Figure B.1 Individual and moving range control chart template 55Figure B.2 Moving mean and moving
13、 range control chart template 56List of tablesTable 1 Key data for constructing a conventional individual and moving range chart 16Table 2 Key constants for control limits 16Table 3 Provisional data for plotting of silicon content in steel 21Table 4 Silicon content in steel data after adjustment 23T
14、able 5 Key data for constructing a moving average mean and moving range chart 27Table 6 Key constants for control limits 27Table 7 % Silicon content provisional data 28Table 8 Key data for constructing a median control chart 31Table 9 Derivation of the medians for spend against budget 31Table 10 Exa
15、mple of construction of cusum chart for % silicon content 34Table 11 Count of system outages per week over a period of one year 43Table 12 Conversion of outage count per month to monthly outage rate 43Table A.1 Strontium-90 in cows milk 46Table A.2 Concentrations of caesium-137 in cows milk in a UK
16、location 48Table A.3 Daily fasting blood sugar levels (mg/dl) 49Table A.4 Project desirables and associated means to improve asthma care 50Table A.5 Daily readings of peak expiratory flow rate (PEFR): Days 110 50Table A.6 Daily readings of peak expiratory flow rate (PEFR): Days 1120 51Table A.7 Dail
17、y readings of peak expiratory flow rate (PEFR): Days 2130 52Table C.1 Proportion of values expected outside of an upper and lower limit in terms of values of capability indices for a normally distributed characteristic 57Summary of pagesThis document comprises a front cover, an inside front cover, p
18、ages i to iv, pages 1 to 58, an inside back cover and a back cover. BSI 2008 iiiBS 5702-2:2008ForewordPublishing informationThis part of BS 5702 was published by BSI and came into effect on 30 April 2008. It was prepared by Technical Committee SS/4, Statistical process control. A list of organizatio
19、ns represented on this committee can be obtained on request to its secretary.Relationship with other publicationsIt is envisaged that, ultimately, BS 5702 will consist of the following parts: Part 0: General introduction to control charts for measurements; Part 1: Charts for mean, median, range and
20、standard deviation; Part 2: Charts for individual values; Part 3: Charting techniques for short production runs and small batches.BS 5702-2 is self-contained in respect to the specific subject matter. It also provides essential links to, and is consistent in approach, format and style with, BS 5702-
21、1 and BS 5702-3, BS 5701 Parts 1 to 4, BS 600 and BS 5703 Parts 1 to 4.Use of this documentBSI permits the reproduction of Figure B.1 and Figure B.2, on pages 55 and 56 of BS 5702-2. This reproduction is only permitted where it is necessary for the user to record findings on the figures during each
22、application of the standard.As a guide, this part of BS 5702 takes the form of guidance and recommendations. It should not be quoted as if it were a specification and particular care should be taken to ensure that claims of compliance are not misleading.Any user claiming compliance with this part of
23、 BS 5702 is expected to be able to justify any course of action that deviates from its recommendations.Presentational conventionsThe provisions in this standard are presented in roman (i.e. upright) type. Its recommendations are expressed in sentences in which the principal auxiliary verb is “should
24、”.Commentary, explanation and general informative material is presented in smaller italic type, and does not constitute a normative element.Contractual and legal considerationsThis publication does not purport to include all the necessary provisions of a contract. Users are responsible for its corre
25、ct application.Compliance with a British Standard cannot confer immunity from legal obligations.iv BSI 2008 This page deliberately left blankBS 5702-2:2008 BSI 2008 1BS 5702-2:20081 ScopeThis part of BS 5702 gives guidance on the application of control charts to individual observations. It demonstra
26、tes the benefits, versatility and usefulness of a simple but powerful pictorial method for monitoring, audit and surveillance with the objectives to control and improve many types of processes. These processes can, for example, be in industry, commerce, public service, health care, environment, food
27、, information technology or finance. Case studies are included to illustrate this adaptability.It describes how and when to apply, select, construct, interpret and use, control charts: generally, to individual measurements of a single characteristic arranged in a meaningful sequence; and specificall
28、y, to particular cases of attribute data.This standard distinguishes between the use of control charts to achieve product control as opposed to steering a process (reducing variation and making estimates of, and securing progressive improvements in, process performance).This standard is aimed at all
29、 those concerned with statistical related initiatives based on individual observations and the continuous improvement of business processes.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated references, only the edition cited ap
30、plies. For undated references, the latest edition of the referenced document (including any amendments) applies.BS 600:2000, Guide to the application of statistical methods to quality and standardizationBS 5702-1, Guide to statistical process control (SPC) charts for variables Part 1: Charts for mea
31、n, median, range and standard deviationBS ISO 3534-2:2006, Statistics Vocabulary and symbols Part 2: Applied statisticsBS 5702-2:20082 BSI 20083 Terms, definitions and symbols3.1 Terms and definitionsFor the purposes of this part of BS 5702, the terms and definitions given in BS ISO 3534-2 apply. Ke
32、y terms and definitions required for the understanding of this standard are reproduced here.3.1.1 Process management3.1.1.1 characteristicdistinguishing featureNOTE 1 A characteristic can be inherent or assigned.NOTE 2 A characteristic can be quantitative or qualitative.NOTE 3 There are various clas
33、ses of characteristic, such as: physical (e.g. mechanical, electrical, chemical, biological); sensory (e.g. relating to smell, touch, taste, sight, hearing); behavioural (e.g. courtesy, honesty, veracity); temporal (e.g. punctuality, reliability, availability); ergonomic (e.g. linguistic or physiolo
34、gical or related to human safety); functional (e.g. range, speed and rate of climb of an aircraft).BS EN ISO 9000:20053.1.1.2 sample statisticsummary measure of some observed value of a sampleNOTE 1 Sample statistics (random variables) are symbolized by upper case Latin letters in italics (e.g. and
35、S) whereas the actual realization of sample statistics (observed values) are symbolized by lower case Latin letters in italics (e.g. and s). This contrasts with population parameters symbolized by lower case Greek letters in italics (e.g. and ).NOTE 2 Observed values may be combined to form a test r
36、esult or measurement result. For instance, the density of a bar may involve the combining of observed values of length, diameter and mass.3.1.1.3 processset of interrelated or interacting activities which transforms inputs into outputsNOTE 1 Inputs to a process are generally outputs from other proce
37、sses.NOTE 2 Processes in an organization are generally planned and carried out under controlled conditions to add value.NOTE 3 A process where the conformity of the resulting product cannot be readily or economically verified is frequently referred to as a “special process”.BS EN ISO 9000:2005Xx BSI
38、 2008 3BS 5702-2:20083.1.1.4 productresult of a processNOTE 1 There are four generic product categories, as follows: services (e.g. transport); software (e.g. computer program, dictionary); hardware (e.g. engine mechanical part); processed materials (e.g. lubricant).Many products comprise elements b
39、elonging to different generic product categories. Whether the product is then called service, software, hardware or processed material depends on the dominant element. For example, the offered product “automobile” consists of hardware (e.g. tyres), processed materials (e.g. fuel, cooling liquid), so
40、ftware (e.g. engine control software, drivers manual), and service (e.g. operating explanations given by the salesman).NOTE 2 Service is the result of at least one activity necessarily performed at the interface between the supplier and customer and is generally intangible. Provision of a service ca
41、n involve, for example, the following: an activity performed on a customer-supplied tangible product (e.g. automobile to be repaired); an activity performed on a customer-supplied intangible product (e.g. the income statement needed to prepare a tax return); the delivery of an intangible product (e.
42、g. the delivery of information in the context of knowledge transmission); the creation of ambience for the customer (e.g. in hotels and restaurants).Software consists of information and is generally intangible and can be in the form of approaches, transactions or procedures.Hardware is generally tan
43、gible and its amount is a countable characteristic. Processed materials are generally tangible and their amount is a continuous characteristic. Hardware and processed materials often are referred to as goods.NOTE 3 Quality assurance is mainly focused on intended product.BS EN ISO 9000:20053.1.1.5 st
44、atistical process controlSPCactivities focused on the use of statistical techniques to reduce variation, increase knowledge about the process and steer the process in the desired wayNOTE 1 SPC operates most efficiently by controlling variation of a process characteristic or an in-process product cha
45、racteristic that is correlated with a final product characteristic; and/or by increasing the robustness of the process against this variation. A suppliers final product characteristic can be a process characteristic to the next downstream suppliers process.NOTE 2 Although SPC originally was concerne
46、d primarily with manufactured goods, it is also equally applicable to processes producing services or transactions, for example, those involving data, software, communications and movement of material.NOTE 3 SPC involves both process control and process improvement.BS 5702-2:20084 BSI 20083.1.1.6 va
47、riationdifference between values of a characteristicNOTE Variation is often expressed as a variance or standard deviation.3.1.1.7 inherent process variationvariation in a process when the process is operating in a state of statistical control3.1.1.8 total process variationvariation in a process due
48、to both special causes and common causes3.1.1.9 special causesource of process variation other than inherent process variationNOTE 1 Sometimes special cause is taken to be synonymous with assignable cause. However a distinction is recognized. A special cause is assignable only when it is specificall
49、y identified.NOTE 2 A special cause arises because of specific circumstances that are not always present. As such, in a process subject to special causes, the magnitude of the variation from time to time is unpredictable.3.1.1.10 random causecommon causechance cause (deprecated)source of process variation that is inherent in a process over timeNOTE 1
