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1、2004考研数学热点问答之概率论与数理统计篇2004probabilityandmathematicalstatisticsofhottopicsinGraduateSchool1.probabilityformula,moreconcepts,howtoremember?Answer:weseesuchamodel,whichisoftenseeninprobability,fromtheactualproductinsideeverytimewetakeaproduct,butnotback,istodrawalotterymodelindailylife・Isaidfour
2、wordsnow,weseewhatisdifferent,thefirstsentencez/forthethreetimetotenproductshavesevenpiecesofthreepiecesofgenuineones,everytimewetakeatakeandnotputback,herewefindfourtypes,wefirstaskedforthirdtimestoobtainthegoodstheprobability・Second,weaskforonlythirdtimestheprobabilityofdefectivegoods・Third
3、ask,knownthefirsttwotimesdidnotgetdefective,thirdtimestopickupdefectivegoods・Fourthasknomorethanthreetimestogetdefectivegoods・Youseethesefourquestions,Ithinkitiseasytoconfused,andthisisfourentirelydifferentprobability,butafteryouread,theremaybemanycandidatesthinkthatthereisatype,butinfactisno
4、tthesame・Firstlookatthefirst"thirdtimesgettingdefective",thisprobabilityhasnothingtodowithwhatisachievedorwhatisachievedlater,sothisiscalledabsoluteprobability・Thefirstprobability,Ithinkmanycandidatesknow,thisprobabilityshouldbeequalto3/10,usingtheancientprobabilityformula,ortheformulaoftotal
5、probabilitytofindout,are3/10.Thisprobabilityischangedtofourthandfifthtimes,anditis3/10.Thatistosay,thisprobabilityhasnothingtodowiththenumberoftimes・Soherewecanseethatindailylifedrawlotsmathematicallyisfair.Takingthismodel,theprobabilityofgettingthefirstandtenthfaultyitemsis3/10.Let'stakealoo
6、kattheprobabilityofthesecondandthethirdchanceofgettingthedefectiveitem.Thiseventdescribestheperformanceevent,whichisanimportantconceptinprobability,whichchangestheprobabilityofsimultaneousoccurrence・However,theprobabilityofthethirdisconfusing,andiftheexpressioncanbeexpressedinthisway,ifAlisus
7、edtoindicatethefirstdefectiveproduct,A2meansthesecondtimetotakethedefectiveproduct・A3isthethirdtotakethedefectiveproduct・IfAmeansthatthefirsttimedoesnottakethedefectiveproduct,theBindicatesthatthesecondtimedoesnottakethedefectiveproduct,andth
