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COMM 291 Assignment 4 Problems

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Question;Question4:AngusReidStrategiessurveyed1016Canadianadults(assumea50/50splitbetween menandwomen)andfoundthat65%ofmenand45%ofwomensupportscrappingthepenny.a) Constructa90%confidenceintervalforthedifferenceinsupportforscrappingthepennybetweenmenandwomen.b) Constructa99%confidenceintervalforthedifferenceinsupportbetweenmenandwomen.c) Interpretthemeaningofthefactthatoneoftheseconfidenceintervalsiswiderthantheother.Question5:In2008,aGallupPollasked2336U.S.adultsaged18oroverhowtheyratedeconomicconditions.InapollconductedfromJanuary27throughFebruary1,2008,24%ratedtheeconomyasExcellent/Good.ArecentmediaoutletclaimedthatthepercentageofAmericanswhofelttheeconomywasinExcellent/Goodshapewas,infact,28%.DoestheGallupPollsupportthisclaim?a) Finda95%confidenceintervalforthesampleproportionofU.S.adultswhoratedtheeconomyasExcellent/Good.Checkconditions.b) Doesyourconfidenceintervalprovideevidencetosupporttheclaim?c) Whatisthesignificancelevelofthetestinpartb)?Explain.Question6:ThesameGallupPolldatafromQuestion5alsoreportedthat33%ofthosesurveyedratedtheeconomyasPoor.Thesamemediaoutletclaimedthetrueproportiontobe30%.DoestheGallupPollsupportthisclaim?a) Finda95%confidenceintervalforthesampleproportionofU.S.adultswhoratedtheeconomyasPoor.Checkconditions.b) Doesyourconfidenceintervalprovideevidencetosupporttheclaim?c) Whatisthesignificancelevelofthetestinpartb)?Explain.Question7:Acompanywithalargefleetofcarshopestokeepgasolinecostsdownandsetsagoalofattainingafleetaverageofatleast26milespergallon.Toseeifthegoalisbeingmet,thecompanychecksthegasolineusagefor50companytripschosenatrandom,findingameanof25.05mpgandastandarddeviationof4.83mpg.Isthisstrongevidencethatthecompanyhasfailedtoattainitsfueleconomygoal?a) Writeappropriatehypotheses.b) Arethenecessaryassumptionstoperforminferencesatisfied?c) TestthehypothesisandfindthePvalued) ExplainwhatthePvaluemeansinthiscontext.e) Stateanappropriateconclusion.Question8:During200811,ViaRailinstallednewpassingtracksandaCentralizedTrafficControlsystemonthelinebetweenKingstonandOttawainordertoreducedelays.Supposethat,beforetheimprovements,trainsbetweenKingstonandOttawawereonaverage12.4minuteslate.Aftertheimprovements,aconsumergroupmonitoreddelaysduringaperiodofthreemonths.Forarandomsampleof35trains,itfoundtheaveragedelaytobe6.2minuteswithastandarddeviationof8minutes.Theimprovementsreduceddelaysbyhalf,theyclaimed.a) Haveaveragedelaysbeenreduced?StateyourhypothesesandcalculateaPvalue.Stateanyassumptionsyouremakingandwhethertheyrelikelytobetrue.b) Calculatethe95%confidenceintervalforthedelaysaftertheimprovements,assumingtheconditionsaresatisfied.Commentonvalidityofyourconfidenceinterval.c) Commentontheethicsoftheconsumergroupsstatement.

 

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