质量管理学CH4

Chapter4SamplingInspection第四章抽样检验QualityInspection一、质量检验QualityInspection1、概念2、质量检验指标（1）单个产品（2）一批产品——批不合格品率——过程平均不合格品率质量认证制度质量认证制度的主要类型认证类型型式试验质量体系评定认证后监督一市场抽样工厂抽样质量体系复查二三四五六七批量检验八100%检验质量检验方法3、质量检验方法（1）全数检验100%Inspection—优点与缺点—适用范围（2）抽样检验SamplingInspection—优点与缺点—适用范围AcceptanceSampling4PurposesDeterminequalitylevelEnsurequalityiswithinpredeterminedlevelAdvantagesEconomyLesshandlingdamageFewerinspectorsUpgradingoftheinspectionjobApplicabilitytodestructivetestingEntirelotrejection(motivationforimprovement)AcceptanceSampling5DisadvantagesRisksofaccepting“bad”lotsandrejecting“good”lotsAddedplanninganddocumentationSampleprovideslessinformationthan100-percentinspectionPrincipleofSamplingInspection二、抽样原理1、抽样检验方案（1）组成抽样方案由三个基本参数组成：N——批量大小，n——样本量，c——不合格品数或产品质量特性不合格的临界值。表示形式为（N，n，c）（2）种类抽样方案
按质量特性分类计数型抽样方案计量型抽样方案
按抽取样本的个数分类一次抽样二次抽样多次抽样序贯抽样抽样特性函数L(p)2、抽样特性函数L(p)设一批产品批量为N，抽样方案是（n|c），该批产品的不合格品率为p，求抽样特性函数L（p）。因批量为N，不合格品率为p，故批中不合格品总数应为Np，记为D=Np，由统计学，从N个中抽取n个样本，其中正好包含d个不合格品的概率为：{} ==nNdnDNdDdxP当采用方案（n|c）抽样时，只要样本中的不合格品数不超过c，则认为该批产品是合格的而被接收，即cd=2,1,0都是允许的，由此我们可以列出该方案的抽样特性函数L（p）：()= = ++ + =cdnNdnDNdDnNcnDNcDnNnDNDnNnDNDpL0110L(p)计算示例例：某批产品N=20，用抽样方案为（1|0）来验收，试计算抽样特性函数L(p)批中的不合格品数不合格品率(%)接收概率批中的不合格品数不合格品率(%)接收概率001.0011550.45150.9512600.402100.9013650.353150.8514700.304200.8015750.255250.7516800.206300.7017850.157350.6518900.108400.6019950.059450.5520100010500.50OperatingCharacteristicCurve不合格品率p接收概率L（p）50%100%1.000.50OperatingCharacteristicCurveOC曲线的两类错误
第一类错误：以概率拒收合格批，为“供货方风险”
第二类错误：以概率接收不合格批，为“需求方风险”抽样检验两类错误α=1-L(p0)1.00p（%）L(p)p0p1β=L(p1)%DefectiveinLotP(AcceptWholeShipment)100%0%Cut-Off123456789100ReturnwholeshipmentKeepwholeshipmentOCCurve100%InspectionP(AcceptWholeShipment)100%0%%DefectiveinLotCut-Off123456789100ReturnwholeshipmentKeepwholeshipmentProbabilityisnot100%:Riskofkeepingbadshipmentorreturninggoodone.OCCurvewithSampling理想的OC曲线100%接收概率L（p）1.00p00不合格品率理想的OC曲线优良的OC曲线0p0p11.00P(%)好坏优良的OC曲线OperatingCharacteristicCurve
OC曲线的变化Ⅰ、N对OC曲线的影响p%NncA100020cB10020cC5020cL(p)1001.00ABC50OperatingCharacteristicCurveⅡ、n对OC曲线的影响p%1001.00L(p)50C=2n=10n=30n=50n=100n=200OperatingCharacteristicCurveⅢ、c对OC曲线的影响1.00L(p)10050n=20c=5c=4c=3c=2c=1c=0P%AcceptanceSampling--SingleSamplingPlanAsimplegoalDetermine(1)howmanyunits,n,tosamplefromalot,and(2)themaximumnumberofdefectiveitems,c,thatcanbefoundinthesamplebeforethelotisrejected.RiskAcceptableQualityLevel(AQL)Max.acceptablepercentageofdefectivesdefinedbyproducer.(Producer’srisk)Theprobabilityofrejectingagoodlot.LotTolerancePercentDefective(LTPD)Percentageofdefectivesthatdefinesconsumer’srejectionpoint.(Consumer’srisk)Theprobabilityofacceptingabadlot.
Acceptablequalitylevel(AQL)QualitylevelofagoodlotProducer(supplier)doesnotwantlotswithfewerdefectsthanAQLrejected
Lottolerance%defective(LTPD)QualitylevelofabadlotConsumer(buyer)doesnotwantlotswithmoredefectsthanLTPDacceptedAQL<PDOperatingCharacteristicCurven=99c=4AQLLTPD00.10.20.30.40.50.60.70.80.91123456789101112PercentdefectiveProbabilityofacceptance=.10(consumer’srisk)=.05(producer’srisk)P(AcceptWholeShipment)100%%DefectiveinLot1234567891000%LTPDb=P(Acceptabadshipment);consumerriskBadLotsAQLGoodLotsa=P(Rejectagoodshipment);producerriskOCCurve&Risk123456789100%DefectiveinLotP(AcceptWholeShipment)100%0%LTPDAQLn=50,c=1n=100,c=2OCCurvesforDifferentSamplingPlansAOQ,AOQLp0.20.40.60.81.0AOQL01.02.03.04.05.06.0抽样后的AOQ曲线ASN曲线ASN1005012345p%一次抽样（75，1）二次抽样（50，100，0，2）百分比抽样的不合理性设有二批产品各为1000与100，不合格品率同为10%，现取方案为抽取5%，合格判定数为c=0，下面计算它们各自的接收概率。①N=1000，p=10%，D=100，n=1000×5%=50，c=0()004476.05010000501001000010001= = =nNcnDNDpL②N=100，p=10%，D=10，n=100×5%=5，c=0()583752.05100051010001001= = =nNcnDNDpLSamplingInspection
计数标准型抽验方案
（1）特点
（2）计数标准型一次抽样检查表
（3）抽验程序
（4）应用实例SingleSampling抽取一个大小为n的样组测定样组中的不合格品数d≤cdc合格，接受不合格，拒收Example:AcceptanceSamplingZypercom,amanufacturerofvideointerfaces,purchasesprintedwiringboardsfromanoutsidevender,Procard.Procardhassetanacceptablequalitylevelof1%andacceptsa5%riskofrejectinglotsatorbelowthislevel.Zypercomconsiderslotswith3%defectivestobeunacceptableandwillassumea10%riskofacceptingadefectivelot.DevelopasamplingplanforZypercomanddeterminearuletobefollowedbythereceivinginspectionpersonnel.SortingItOutForthisexample,howdowedetermineAQL??LTPD??Example:ContinuedLTPDAQL=.03.01=3n(AQL)=3.286ExhibitExhibitcLTPD/AQLnAQLcLTPD/AQLnAQL044.8900.05253.5492.613110.9460.35563.2063.28626.5090.81872.9573.98134.8901.36682.7684.69544.0571.97092.6185.426Howcanwedeterminethevalueofn?Whatisoursamplingprocedure?Example:Continuedc=6,fromTablen(AQL)=3.286,fromTableAQL=.01,giveninproblemn(AQL/AQL)=3.286/.01=328.6,or329(alwaysroundup)SamplingProcedure:Takearandomsampleof329unitsfromalot.Rejectthelotifmorethan6unitsaredefective.DoubleSampling抽取样本n1检验n1中的不合格品数d1d1+d2≤c2d1＞c2d1≤c1抽取样本n2检验n2中的不合格