11-Measure+Step+02-A+(Intro+to+SPC).ppt

IntroductiontoStatisticalProcessControl(SPC),Process=Hose,FourImportantProperties:(1)Centering(2)Spread(3)Shape(4)StabilityOverTime,Whathaschanged?Centering?_Spread?_,Whathaschanged?Centering?_Spread?_,Bubbaisknownas“ThestraightestdriverinCrickCounty”.OneeveningatCharliesBar,heboasted,”Idrivesostraight,evenaquartofMoonshinewontthrowmeofftarget”Fed-up,Juniortoldhimto“puthismoneywherehismouthis”-a$100bet.TheyselectedCharlie,thebarowner,tobetheimpartialgumdropper.,TheScene:,Youmakethecall:DidBubbastaystraightorloose$100?,Juniorsays,“Mygosh,itlookslikeyouwereswervingallovertheplacerightfromthebeginning!”“Wheresmy$100?”,CONSIDERTHIS.,.evenwhenCharlieistryinghisbest!,Nowwhatdoyouthink:DidBubbastaystraightorloose$100?,Wouldntitbehelpfultohavesomewayofseparatingthesteeringvariationfromthenatural,inherent“Aim-to-Aim”Variation?,SourcesofVariation:-NaturalAim-to-AimVariation,Wecanstrategicallyusethisnatural,unavoidablevariation(i.e.,thespreadwidth)asatoolfordetectingshiftsinthetruckscentering.,TheControlChartApproach,-AimVariation(only),SourcesofVariation,-AimVariation-VariationDuetoSteering,SourcesofVariation,Thatshowcontrollimitsseparatesignalsfromnoise,UCL,LCL,Noevidenceofanychangesinthetrue“centering”ofthetruck.Allthe“wiggling”ofthedatapointswassimplyduetonoise.,20,30,In-ProcessInventory(X),10,JFMA,1994,1995,April1994:Managerpleasedtoseethein-processinventorydropto15.ManagerpresentsanawardtoDept.50inhonorofthisachievement.Ceremonyinthecafeteria:pizzaandrefreshmentsforall!“Everyoneshouldbeproudofwhatyouveaccomplished”.,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.NiceGuystuffdoesntwork”,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,theydontknowwhattodo.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”youvebeeninthepast-noiseisstillnoise.Tryingtointerpretnoiseisnothingmorethananexerciseinwishfulthinking.Theresult-purefictionwithnoconnectiontoreality.,DerivedfromUnderstandingVariation:TheKeyToManagingChaos,DonaldJ.Wheeler,SPCPress.1993.,“Failuretousecontrolchartstoanalyzedataisoneofthebestwaysknowntomankindtoincreasecosts,wasteeffort,andlowermorale.”-Dr.DonaldJ.Wheeler,“Itsnotwhatwedontknowthathurts.itswhatweknowthataintso.”-WillRogers,Falselessonscostus-bettertoknowhowtousedatawisely!,DerivedfromUnderstandingVariation:TheKeyToManagingChaos,DonaldJ.Wheeler,SPCPress.1993.,VideoSegment,(Optional),Watchhowonemanagersdecisionsandactionsareaffectedwhenheincorrectlyinterprets.,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!Imverydisappointedinyourperformance.Youwereoncemybestsalesrepresentative.Ihadhighexpectationsforyou.Now,Icanonlyhopethatourfirstquarterresultsshowsomesignoflife.”Kimfeltherfacegetred.Sheknewshesoldmoreunitsin1996thanin1995.“WhatdoesHalgerknowanyway,”shethoughttoherself.“Hesjustanemptysuit.”,802807781,SelitCorp.s4thQuarterSalesReport.,Mid-Atlantic,Haglercontinued:“Terry,Southwestsalesweresuper.Youshowedan11.7%increaseinthefourthquarterandan11.8%increaseoverthepreviousyear”-Anupwardtrend!Terrysmiled.Shewasntsurehowshedidsowell,butshesurewasntgoingtochangeanything.,119611971337,SelitCorp.s4thQuarterSalesReport.,SouthWest,Trackingprocessbehaviorbywayofsamplemeasurements(plottedpoints)canbethoughtofasbeingmuchliketrackingarabbitbywayofitsdroppings.Supposethefootball-shapeddroppingsfallatregular1minuteintervals,andwhentheyhittheground,theytendtorollaroundabit(likerandom/samplingvariation).Sothegamebecomes,Howtousestatisticaltoolsasreliableindicators-tokeepusfrombeingfooledbythewobbling(noise)thatwillalwaysbepresentinthedroppings(data)-sowereliablydetectwhethertherabbitdidordidnotmovetotheleftorrightofthestraightpath.,Whencommunicatingstatisticalconcepts,youcoulddescribeSPCasfollows:,Incaseyoumightdaretousetheideaoneday.,Herearesomerules/principlestohelpusknowwhentoreact.,(1)PointbeyondUCLorLCL(+/-3StdDevs)(2)7consecutivepointsonthesamesideofthecenterline(Minitabuses9)(3)Trend:6consecutivepointssteadilyincreasingordecreasing(4)Repeatedpatterns/cycles,HowtoDetectaChangeinProcessBehavior:(i.e.,WhenanXjustmadeanimpactoftheprocess),WecanaskMinitabtosearchfor8outofcontrolconditionsautomatically,X-Bar&RangeChartforWheeler“Master”Data,File:“Wheel_G.mtw”,Letsseehowwecanplot3or4points.,HeresablankXbar&Rchart(forfutureuse),ThisishowaControlChartactuallylooksusingMinitab,Asubtlebutcrucialdistinction:Co