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首页 IGCSE-Statistics 统计学03900390_w03_er

IGCSE-Statistics 统计学03900390_w03_er.pdf

IGCSE-Statistics 统计学03900390_w0…

jennifer__jie
2012-03-04 0人阅读 举报 0 0 0 暂无简介

简介:本文档为《IGCSE-Statistics 统计学03900390_w03_erpdf》,可适用于高等教育领域

Mathematics:Statistics(HalfCredit)NovemberCONTENTSMATHEMATICS:STATISTICS(HALFCREDIT)PaperPaperhttp:wwwxtremepapersnetMathematics:Statistics(HalfCredit)NovemberMATHEMATICS:STATISTICS(HalfCredit)PaperPaperGeneralcommentsThisPaperproducedawiderangeofmarksMostcandidateshadcoveredtheSyllabusadequatelywithonlyafewCentresgainingconsistentlylowmarksPrematureapproximationleadingtoalossofmarkswasonlywitnessedinafewscripts,mostcandidatesrealisingthenecessityofworkingwithfoursignificantfiguresOneunforeseenproblemwasthecandidates’failuretoappreciatethedifferencebetweendecimalplacesandsignificantfiguresThiswasparticularlynoticeableinanswerssuchasand,wheremanygaveanswersasetcCandidatesseemedtohavesufficienttimetoanswerallthequestions,andonlytheweakercandidatesansweredquestionsoutoforderCommentsonspecificquestionsQuestionThisquestioncausedproblemsformanycandidatesManycandidatesconfusedthiswithabinomialsituationandtriedtofindan‘n’anda‘p’Othersfoundfxforthevariance,andasusual,somecandidatesfoundthestandarddeviationAnswers:,QuestionApproximatelyhalfthecandidatesappreciatedtheneedtofindascaledfrequency,orfrequencydensityItwaspleasingtoseemostcandidateshadtouchingbarsonthehistogram,withtheverticalaxislabelledasfrequencydensity,butonlyasmallnumberlabelledthehorizontalaxisasbeingareaormandthusmanycandidateslostamarkQuestionApartfromafewCentreswherethenormaldistributiondidnotappeartohavebeentaughtwithanyrigour,thisquestionwaswelldonewithmostcandidatesfindinganappropriatezvalueTherangeofzvalueswaswiderthanexpected,withmanyrangingfromtoforΦ()OnlyvaluesofandwereacceptedSolvingthesimultaneousequationswaswelldoneandalmostallcandidateswhohaddonesomeworkonthenormaldistributionscoredatleastmarksoutofAnswers:,QuestionThisquestionwastheworstattemptedonthePaperAtreediagramwouldperhapshavehelpedManycandidateswroteinsteadof,manythoughtitwasa‘withoutreplacement’typeofquestionandmanymisunderstoodthelastpartasmeaning‘completeshiscollectionwithlessthanpictures’Answers:(i)(ii)(iii)Mathematics:Statistics(HalfCredit)NovemberQuestionThetreediagramwaswelldrawnbythemajorityofcandidatesAfewfailedtorealisethatthemalefemalebranchhadtocomefirst,andmanymultipliedtheirprobabilitiestogetherbeforewritingthesecondprobabilitiesonthetreediagram,andthenproceededtomultiplyathirdtimeAminorityofthecandidatesappreciatedthatthiswasaconditionalprobabilityquestionandthusmanyscoredonlymarksoutofAnswer:QuestionThispermutationandcombinationquestionwasverywellattemptedbyalmostallcandidates,manypickingupormoremarksSometimestheanswerswerenotintegers,andoccasionallytheybecameprobabilitiesTheanswerswerenotalwaysfullycorrect,butthereweresignsofsensiblereasoningAnswers:(a)(i),(ii)(b)(i),(ii)QuestionThisverystraightforwardnormaldistributionfirstpartgainednearlyfullmarksforeveryonewhohadstudiedthesubjectHowever,quiteafewlostthefinalmarkforthispartbecauseofincorrectuseofthefourfigureNormaltablesThesecondpartwasabinomialsituationbasedonthefirstpart,theanswerofwhichhadalreadybeencalculatedAlmostwithoutexception,candidatescalculatedtheprobabilityalloveragain,suggestingtheyhadnotappreciatedthesignificanceofwhattheyweredoinginpart(i)Theanswerstopart(iii)werealmostallwrongCandidatesclearlydidnotappreciatethedifferencebetween‘mean’and‘median’NeitherdidtheyrealisethatanormaldistributionissymmetricwiththemeanandmediancoincidingAnswers:(i)()(ii)(iii)boxplotisskew,notsymmetricsonotnormalQuestionThisquestionwastheeasiestquestionbyfarandwaswelldonebyalargemajorityForsomeitprovidedhalftheirmarksRoundingerrorsandprematureapproximationledtoafewmarksbeinglost,andnoteveryonerealisedthatpart(iii)entailedaddingprobabilitiesfortwodiscretenumbersAnswers:(i)or(ii),(iii)

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