可疑值的取舍-Trade-offs for doubtfu

可疑值的取舍Trade-offsfordoubtfulvalues知识点

pointofknowledge01可疑值的概念Theconceptofdoubtfulvalue02可疑值检验方法Suspiciousvaluetestmethod一、可疑值的概念II.Theconceptofdoubtfulvalue可疑值：在一组平行测定数据中，有时会有个别测定值偏离其他测定值较远，该值称为可疑值或离群值。Suspiciousvalue:Inasetofparallelmeasurementdata,sometimestherewillbeindividualmeasurementvaluedeviatesfromtheothermeasurementvaluefarther,thevalueiscalledsuspiciousvalueoroutliers.一、可疑值的概念Ⅱ.Theconceptofdoubtfulvalue过失造成：保留数据会严重影响分析结果准确度和精密度，应剔除可疑值。Causedbynegligence:

Retaineddatacanseriouslyaffecttheaccuracyandprecisionofanalyticalresults,andsuspiciousvaluesshouldbe

excluded.随机误差造成：舍弃数据会造成数据的浪费，不能随意舍弃，应进行统计检验来取舍。Randomerrorsarecausedby:roundingoffdatawillresultinwasteddataandshouldnotbedonearbitrarily,statisticaltestsshouldbeperformedtoroundoff.对可疑值应做出如下判断：Thefollowingjudgmentsshouldbemadeaboutsuspectvalues:二、可疑值检验方法ⅡMethodologyofthedoubtfulvaluetestQ检验法QTestmethod可疑值的检验方法Testsfordoubtfulvalues

Grubbs检验法GrubbstestQ检验法QTestmethod①将测定值按递增顺序排列①Arrangethemeasuredvaluesinincreasingorder.②计算测定值的极差（即最大值与最小值之差）②Calculatetheextremedeviationofthemeasuredvalue(i.e.,thedifferencebetweenthemaximumandminimumvalues)③计算可疑值与其相邻值之差③

Calculatethedifferencebetweenthesuspectedvalueanditsneighboringvalues.④可疑值与最邻近数据之差，除以极差，所得的商称为Q计值④Thedifferencebetweenthesuspectvalueandthenearestneighboringdata,dividedbytheextremedeviation,andtheresultingquotientiscalledtheQ-metervalue二、可疑值检验方法Ⅱ.Methodologyofthedoubtfulvaluetest查Q值表，将Q计与Q表相比：ChecktheQ-valuetableandcomparetheQ-metertotheQ-table:二、可疑值检验方法Ⅱ.MethodologyofthedoubtfulvaluetestQ检验法QTestmethodQ计＞Q表

舍弃Q-meter>Q-meter

giveupQ计

≤Q表

保留Qmeter≤Qtable

Reserved3.59偏离其他数值较大，为可疑值，用Q检验法判断有无可疑值需舍弃。3.59Alargedeviationfromothervaluesisasuspiciousvalue,andtheQ-testisusedtodetermineifthereisasuspiciousvaluetobediscarded.例题1Example1ⅠⅡⅢⅣⅤ测得值measuredvalue3.183.323.223.593.34二、可疑值检验方法Ⅱ.Methodologyofthedoubtfulvaluetest解：Solution:将测定数据按大小顺序排列：3.18、3.22、3.32、3.34、3.59Putthemeasurementsinorderofmagnitude:3.18,3.22,3.32,3.34,3.59例题解析exampleanalysis判断可疑值出现的位置：可疑值出现在末项Determinationofthelocationofthesuspiciousvalue:thesuspiciousvalueappearsattheendoftheitem二、可疑值检验方法Ⅱ.Methodologyofthedoubtfulvaluetest

二、可疑值检验方法Ⅱ.Methodologyofthedoubtfulvaluetest例题解析exampleanalysis测定次数Numberofmeasurements345678910Q0.900.940.750.640.560.510.470.440.41舍弃可疑数据的Q值表（置信度为90%）TableofQ-valuesfordroppingsuspectdata(witha90%confidencelevel)Q计（0.61）＜

Q表

（0.64）

保留Qmeter(0.61)<Qtable(0.64)

Reserved二、可疑值检验方法Ⅱ.Methodologyofthedoubtfulvaluetest

三、可疑值的取舍Ⅲ.Trade-offsbetweendoubtfulvalues用EDTA滴定某试剂中的Zn，消耗EDTA体积（mL）分别为：26.32，26.40，26.44，26.42，问26.32这个数据是否应保留？ThevolumeofEDTAconsumed(mL)fortitrationofZninareagentwithEDTAis26.32,26.40,26.44,and26.42,andaskwhetherthefigureof26.32shouldberetained?例子examples三、可疑值的取舍Ⅲ.Trade-offsbetweendoubtfulvalues例子examples

可疑值与平均值的绝对差值为：Theabsolutedifferencebetweenthesuspectvalueandthemeanvalueis:

故26.32这一数据应舍弃Therefore,thefigureof26.32shouldbediscarded科学态度scientificattitude数据处理要尊重科学规律Dataprocessingshouldrespectthelawsofscience环境监测environmentalmonitoring食品安全检测FoodSafetyTesting食品安全问题Foodsafetyissues用科学的态度和方法来处理数据Scientificapproachandmethodologytodata食品安全问题Foodsafetyissues用科学的态度和方法来处理数据ScientificapproachandmethodologytodataCaseReviewInSeptember2020,theMarketSupervisionAdministrationofGlossyCountyfoundthatChenMouhadover-addedalumduringtheproductionofsweetdoughnutsinthesamplingofsweetandsaltydoughnutsproducedandsoldbyChenJi,andthealuminumresidueinthedoughnutswas737mg/kg,whichwasseriouslyexceedingthenationalstandardlimit(≤100mg/kg).NanpingMunicipalMarketSupervisionBureauissuedthe“foodsafetyhazardsidentifiedexpertopinion”thatthesamplingsamples,aluminumresidueissufficienttocauseseriousfoodpoisoningorothersevereelectricalsourceofdisease.CasestatementThecourtheldthatChenMouviolatedfoodsafetystandards,intheprocessoffoodproductionandsales,overthelimitoftheabuseoffoodadditives,enoughtocauseseriousfoodpoisoningorotherseriousfood-borneillnesses,andhisbehaviorconstitutesthecrimeofproductionandsaleoffoodthatdoesnotmeetthesafetystandards,andthecrimeofproductionandsaleoffoodthatdoesnotmeetthesafetystandards,andthecrimeofproductionandsaleoffoodthatdoesnotmeetthesafetystandards.PopularKnowledgeAlumisatraditionalfoodimproverandbulkingagent,however,itschemicalcompositionispotassiumaluminumsulfate,containingaluminumions,exce