数据分析2(3)

YousubmittedthisquizonMon3Mar20146:15AMPST.Yougotascoreof8.00outof12.00.Question1Whichofthefollowingexplainsthephenomenonthatwhilein10flipsofafaircoinitmaynotbeverysurprisingtoget8Heads,itwouldbeverysurprisingtoget8,000Headsin10,000flipsofthecoin.YourAnswerScoreExplanationGeneraladditionruleBayes’theoremLawoflargenumbersLawofaveragesInorrect0.00Total0.00/1.00QuestionExplanationThisquestionreferstothefollowinglearningobjective:Explainwhythelong-runrelativefrequencyofrepeatedindependenteventssettlesdowntothetrueprobabilityasthenumberoftrialsincreases,i.e.whythelawoflargenumbersholds.Question2ShownbelowarefourVenndiagrams.InwhichofthediagramsdoestheshadedarearepresentAandBbutnotC?YourAnswerScoreExplanationCorrect1.00WeneedtheareacommontoeventsAandBtobeentirelyshadedexceptforthatportioncommontoeventC:“AandBbutnotC”.Total1.00/1.00QuestionExplanationThisquestionreferstothefollowinglearningobjective:DrawVenndiagramsrepresentingeventsandtheirprobabilities.Question3Whichofthefollowingisfalseaboutprobabilitydistributions?YourAnswerScoreExplanationTheprobabilitiesmusttotal1.Theoutcomeslistedmustbeindependent.Correct1.00Thereisnosuchrestrictionthatwemustonlylistindependentoutcomes.Eachprobabilityshouldbelessthanorequalto1.Eachprobabilityshouldbegreaterthanorequalto0.Total1.00/1.00QuestionExplanationThisquestionreferstothefollowinglearningobjective:Defineaprobabilitydistributionasalistofthepossibleoutcomeswithcorrespondingprobabilitiesthatsatisfiesthreerules:-Theoutcomeslistedmustbedisjoint.-Eachprobabilitymustbebetween0and1.-Theprobabilitiesmusttotal1.Question4Lastsemester,outof170studentstakingaparticularstatisticsclass,71studentswere“majoring”insocialsciencesand53studentsweremajoringinpre-medicalstudies.Therewere6studentswhoweremajoringinbothpre-medicalstudiesandsocialsciences.Whatistheprobabilitythatarandomlychosenstudentismajoringinsocialsciences,giventhats/heismajoringinpre-medicalstudies?YourAnswerScoreExplanation(71+53−6)/1706/53Correct1.00IfMistheeventastudentismajoringinpre-medicalstudiesandSistheevents/heismajoringinsocialsciences,thencalculateP(S|M)=P(S&M)P(M)=653.6/716/170Total1.00/1.00QuestionExplanationThisquestionreferstothefollowinglearningobjective:Distinguishmarginalandconditionalprobabilities.Question5Whichofthefollowingstatementsisfalse?YourAnswerScoreExplanationTwodisjointoutcomes(ofthesameevent)cannotoccuratthesametime.Twomutuallyexclusiveoutcomes(ofthesameevent)cannotoccuratthesametime.Twoindependenteventscannotoccuratthesametime.Correct1.00Independenteventsarenotnecessarilymutuallyexclusive.Twocomplementaryoutcomes(ofthesameevent)cannotoccuratthesametime.Total1.00/1.00QuestionExplanationThisquestionreferstothefollowinglearningobjective:•Definedisjoint(mutuallyexclusive)eventsaseventsthatcannotbothhappenatthesametime:IfAandBaredisjoint,P(AandB)=0.•Distinguishbetweendisjointandindependentevents.-IfAandBareindependent,thenhavinginformationonAdoesnottellusanythingaboutB(andviceversa).-IfAandBaredisjoint,thenknowingthatAoccurstellsusthatBcannotoccur(andviceversa).-Disjoint(mutuallyexclusive)eventsarealwaysdependentsinceifoneeventoccursweknowtheotheronecannot.Question6SupposeIQscoresarenormallydistributedwithmean100andstandarddeviation10.Whichofthefollowingisfalse?YourAnswerScoreExplanationAnIQscoreof80ismoreunusualthananIQscoreof120.Correct1.00Thescoresof80and120arethesamedistance(2standarddeviations)fromthemean(100)ofthedistribution.Becausethenormaldistributionissymmetric,thesescoresareequallylikely.AnIQscoregreaterthan130ishighlyunlikely,butnotimpossible.Roughly68%ofpeoplehaveIQscoresbetween90and110.AnormalprobabilityplotofIQscoresofarandomsampleof1,000peopleshouldshowastraightline.Total1.00/1.00QuestionExplanationThisquestionreferstothefollowinglearningobjective:UsetheZscore-ifthedistributionisnormal:todeterminethepercentilescoreofadatapoint(usingtechnologyornormalprobabilitytables)-regardlessoftheshapeofthedistribution:toassesswhetherornottheparticularobservationisconsideredtobeunusual(morethan2standarddeviationsawayfromthemean)Question7A2005surveyfoundthat7%ofteenagers(ages13to17)sufferfromanextremefearofspiders(arachnophobia).Atasummercampthereare10teenagerssleepingineachtent.Assumethatthese10teenagersareindependentofeachother.Whatistheprobabilitythatatleastoneofthesuffersfromarachnophobia?YourAnswerScoreExplanation82%52%Correct1.00WeareaskedforP(k≥1|n=10,p=0.07).Noticethisisequalto1−P(k=0|n=10,p=0.07).Thelatteriseasiertocalculatesinceitonlyrequiresonecalculationusingthebinomialdistribution.So,weusethebinomialdistributionwithn=10,k=0,andp=0.07andcalculateP(k≥1|n=10,p=0.07)=1−P(k=0|n=10,p=0.07)=1−()0.0700.9310=1−0.4840=0.516.062%42%72%Total1.00/1.00QuestionExplanationThisquestionreferstothefollowinglearningobjective:Calculatetheprobabilityofagivennumberofsuccessesinagivennumberoftrialsusingthebinomialdistribution.Question8Youareabouttotakeamulti-daytourthroughanationalparkwhichisfamousforitswildlife.Thetourguidetellsyouthatonanygivendaythere’sa61%chancethatavisitorwillseeatleastone“biggame”anima