The Effect of Estimated Parameters on Poisson EWMA Control Charts

摘要

Performanceofcontrolchartsisgenerallyevaluatedwiththeassumptionthattheprocessparametersareknown.Inmanycontrolchartapplications,however,theprocessparametersarerarelyknownandtheirestimatesfromanin-controlreferencesampleareusedinstead.Insuchcases,themomentsoftherunlengthdistributiondependonthevaluesoftheestimatedparameters.ThePoissonexponentiallyweightedmovingaverage(EWMA)isaneffectivecontrolchartinsituationswherethenumberofnonconformitiesperunitfromarepetitiveproductionprocessismonitored.TheobjectiveofthispaperistostudytheeffectofestimatingthemeanontheperformanceofthePoissonEWMAcontrolchart.WemakeuseoftheMarkovChainapproach.Sample-sizerecommendationsandsomeconcludingcommentsareprovided.