MeasureStepA(IntrotoSPC)（英文版）.ppt

IntroductiontoStatisticalProcessControl SPC Process Hose FourImportantProperties 1 Centering 2 Spread 3 Shape 4 StabilityOverTime Whathaschanged Centering Spread Whathaschanged Centering Spread Bubbaisknownas ThestraightestdriverinCrickCounty OneeveningatCharlie sBar heboasted Idrivesostraight evenaquartofMoonshinewon tthrowmeofftarget Fed up Juniortoldhimto puthismoneywherehismouthis a 100bet TheyselectedCharlie thebarowner tobetheimpartialgumdropper TheScene Youmakethecall DidBubbastaystraightorloose 100 Juniorsays Mygosh itlookslikeyouwereswervingallovertheplacerightfromthebeginning Where smy 100 CONSIDERTHIS evenwhenCharlieistryinghisbest Nowwhatdoyouthink DidBubbastaystraightorloose 100 Wouldn titbehelpfultohavesomewayofseparatingthesteeringvariationfromthenatural inherent Aim to Aim Variation SourcesofVariation NaturalAim to AimVariation Wecanstrategicallyusethisnatural unavoidablevariation i e thespreadwidth asatoolfordetectingshiftsinthetruck scentering TheControlChartApproach AimVariation only SourcesofVariation AimVariation VariationDuetoSteering SourcesofVariation That showcontrollimitsseparatesignalsfromnoise UCL LCL Noevidenceofanychangesinthetrue centering ofthetruck Allthe wiggling ofthedatapointswassimplyduetonoise 20 30 In ProcessInventory X 10 JFMA 1994 1995 April1994 Managerpleasedtoseethein processinventorydropto15 ManagerpresentsanawardtoDept 50inhonorofthisachievement Ceremonyinthecafeteria pizzaandrefreshmentsforall Everyoneshouldbeproudofwhatyou veaccomplished DerivedfromUnderstandingVariation TheKeyToManagingChaos DonaldJ Wheeler SPCPress 1993 20 30 In ProcessInventory X 10 JFMAMJJ 1994 1995 July1994 Threeconsecutivemonthsofinventoryincreases Managerwisheshecouldtakebacktheaward Recognitionseemstohavebeenbackfired Insteadofholdingthegains Dept 50seemstohavegottencomplacent allowinginventorytocreepbacktowhereitwaspreviously Managerdecides ThisMr NiceGuystuffdoesn twork DerivedfromUnderstandingVariation TheKeyToManagingChaos DonaldJ Wheeler SPCPress 1993 20 30 In ProcessInventory X 10 JFMAMJJASOND 1994 1995 NomoreMr NiceGuy Nov 1994 In processinventoryrisestoavalueof26 Managerdecidestokickanatomyandtakenames Hecallseveryoneinanddemandstheydosomethingtokeepinventoriesdown Followingthistantrum everyoneinDept 50treadslightly Shortofhidingmaterialinthedarkcornersoftheplant theydon tknowwhattodo So theyholdtheirbreathandhopeinventoriesdrop DerivedfromUnderstandingVariation TheKeyToManagingChaos DonaldJ Wheeler SPCPress 1993 June1995 Managerhasseenreducedlevelsofinventorysincetheendoflastyear Thingsarelooking up Althoughnothinghadbeendonetochangethesystem Hislearning Toughmanagementstylegetsresults Managerconcludes Toughmanagementstylegetsresults 20 30 In ProcessInventory X 10 JFMAMJJASOND 1994 1995 JFMAMJ DerivedfromUnderstandingVariation TheKeyToManagingChaos DonaldJ Wheeler SPCPress 1993 ButIalwaysmadesuremydecisions actionswerebasedondata Whatcouldbewrongwiththat Hisdecisionsstemmedfrominterpretingthehighandlowpointsassignals However asthecontrolchartbelowclearlyreveals NONEOFTHESEINDIVIDUALPOINTSWERESIGNALS Theyallreflectthesameunderlyingsystem eachshouldbeinterpretedalike DerivedfromUnderstandingVariation TheKeyToManagingChaos DonaldJ Wheeler SPCPress 1993 Nomatterhowlogicalandpersuasivetheinterpretation andnomatterhow right you vebeeninthepast noiseisstillnoise Tryingtointerpretnoiseisnothingmorethananexerciseinwishfulthinking Theresult purefictionwithnoconnectiontoreality DerivedfromUnderstandingVariation TheKeyToManagingChaos DonaldJ Wheeler SPCPress 1993 Failuretousecontrolchartstoanalyzedataisoneofthebestwaysknowntomankindtoincreasecosts wasteeffort andlowermorale Dr DonaldJ Wheeler It snotwhatwedon tknowthathurts it swhatweknowthatain tso WillRogers Falselessonscostus bettertoknowhowtousedatawisely DerivedfromUnderstandingVariation TheKeyToManagingChaos DonaldJ Wheeler SPCPress 1993 VideoSegment Optional Watchhowonemanager sdecisionsandactionsareaffectedwhenheincorrectlyinterprets NOISE typical inherent minute to minuteprocessvariationbehavior SIGNAL clearlydifferentbehavior aboveandbeyondtheusualnoise asifitwerea Doyouknowanyoperators co workers ormanagerswhohavemanagedprocessesthisway Year Smokers198418 8198519 6198618 7198718 6198818 1198918 9199019 2199118 2199217 3199319 0 93 92 91 90 89 88 87 86 85 84 21 20 19 18 17 16 Year Individuals X 18 64 UCL 20 71 LCL 16 57 3 2 1 0 MovingRange R 0 7778 UCL 2 541 LCL None IandMRChartfor Smokers Openminitabworksheetfile Sales QuarterlyData mtw Kim Mid Atlanticsalesweredown3 2 inthefourthquarteranddown2 6 fromthepreviousyear adownwardtrend I mverydisappointedinyourperformance Youwereoncemybestsalesrepresentative Ihadhighexpectationsforyou Now Icanonlyhopethatourfirstquarterresultsshowsomesignoflife Kimfeltherfacegetred Sheknewshesoldmoreunitsin1996thanin1995 WhatdoesHalgerknowanyway shethoughttoherself He sjustanemptysuit 802807781 SelitCorp s4thQuarterSalesReport Mid Atlantic Haglercontinued Terry Southwestsalesweresuper Youshowedan11 7 increaseinthefourthquarterandan11 8 increaseoverthepreviousyear Anupwardtrend Terrysmiled Shewasn tsurehowshedidsowell butshesurewasn tgoingtochangeanything 119611971337 SelitCorp s4thQuarterSalesReport SouthWest Trackingprocessbehaviorbywayofsamplemeasurements plottedpoints canbethoughtofasbeingmuchlike trackingarabbitbywayofitsdroppings Supposethefootball shapeddroppingsfallatregular1minuteintervals andwhentheyhittheground theytendtorollaroundabit likerandom samplingvariation Sothegamebecomes Howtousestatisticaltoolsasreliableindicators tokeepusfrombeingfooledbythe wobbling noise thatwillalwaysbepresentinthedroppings data sowereliablydetectwhethertherabbitdidordidnotmovetotheleftorrightofthestraightpath Whencommunicatingstatisticalconcepts youcoulddescribeSPCasfollows Incaseyoumightdaretousetheideaoneday Herearesomerules principlestohelpusknowwhentoreact 1 PointbeyondUCLorLCL 3StdDev s 2 7consecutivepointsonthesamesideofthecenterline Minitabuses9 3 Trend 6consecutivepointssteadilyincreasingordecreasing 4 Repeatedpatterns cycles HowtoDetectaChangeinProcessBehavior i e WhenanXjustmadeanimpactoftheprocess WecanaskMinitabtosearchfor8outofcontrolconditionsautomatically X Bar RangeChartforWheeler Master Data File Wheel G mtw Let sseehowwecanplot3or4points Here sablankXbar Rchart forfutureuse ThisishowaControlChartactuallylooksusingMinitab Asubtlebutcrucialdistinction Controllimits