Receiver Operating Characteristic (ROC) Curve Analysis.pdf

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1、ReceiverOperatingCharacteristic(ROC)CurvesReceiverOperatingCharacteristic(ROC)CurveAnalysis•Developedin1940’stomakesenseofradiosignals,usedbyradarreceiverstoAusefultooltoevaluatetheeffectivenessofbeachpostingpoliciesanalyzeradarimagesduringWorldWarII•Beginninginthe1970’s,recognizeda

2、susefulforinterpretingmedicaltestKellyCoughlinresultsMassachusettsWaterResourcesAuthority•SimpletouseBoston,MAOverviewBeachManagementConcerns1.DescriptionofROCanalysis•Needtoregulatebeachusageonadailybasis2.Walk-throughconstructinganROCcurve•Measuringbacteriaisinformative,butadaylat

3、e;resultsarenotavailableinreal-time3.Implicationsformonitoringandmanagement•Bacteriacountsfluctuate,ameasurementmadethepreviousdaymaynotaccuratelyreflectcurrentconditionsEffectivenessofpreviousday’sAperfecttest…ornotEnterococcustotriggerswimmingadvisoriesActualWaterQualityFailstomee

4、tMeetsAverage#TrueFalseFalseswimmingSwimmingBeachofdaysinaPositivesnegativespositivesstandardsStandardsseasion(actualalarm)(missedalarm)(falsealarm)CityPointBeach,70days0days2days2daysSwimmingFalsePositiveSouthBostonTruePositiveAdvisory(FalseAlarm)ConstitutionBeach,East70days1-2days

5、2days2daysBostonFalseNoWollastonSwimmingNegativeTrueBeach,70days6days13days13daysAdvisoryStatus(MissedNegativeQuincyAdvisoryAlarm)Resultsfrom2000–2005swimmingseasons.Previousday’sEnterococcuscountof104cfu/100mLtriggersaswimmingadvisory.1ComparingtheeffectivenessofotherTestingtoident

6、ifytwoconditionsswimmingadvisorytriggers+GoodwaterTestthresholdvaluequality•Setasagiventhatwaterqualityconditions(conditionsmeetingPoorwateraremeasuredbyEPAswimmingstandardsstandards)quality(conditionsfailtomeetstandards)•WeselectedrainfallasanalternativetestRelativefrequencyofcondi

7、tionofinterestsincerunoffisaknowncauseofelevatedPossibleTestValuesbacteriacountsatHarborbeaches•Twoactualconditionsexistthatthetestattemptsto•Howdoesarainfallthresholdcomparetoidentifypreviousday’sEnterococcusin–GOODWATERQUALITY-POORWATERQUALITYeffectiveness?•Atestusesasinglevalueto

8、identifytheconditio