ECMT 5001 Year Semester 2REVISIONQUES08.docx
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ECMT5001YearSemester2REVISIONQUES08
Econometrics&BusinessStatistics
ECMT5001:
PrinciplesofEconometrics
RevisionQuestions.
Pleasenotethatthesequestionsarerevisionquestionsandmaynotbeinthesamestyleastheexaminationquestions.Thesequestionswillallowyoutotestyourknowledgeofthebasicconceptsintheunitofstudy.
PART1:
Q.1Aventurecapitalcompanyfeelsthattherateofreturn(X)onaproposedinvestmentisapproximatelynormallydistributedwithameanof30%andastandarddeviationof10%.(Hint:
Usethepercentagesasawholenumber.Donotuseasaproportion.)
Findtheprobabilitythat
a)thereturnwillexceed55%.
b)thereturnwillbelessthan22%.
c)thereturnwillbebetween21%and29%.
d)theaveragereturnwillbelessthan34%ifasampleof20istaken.
Q.4LetXrepresentthenumberofmachinefailuresforanygivendaybytwoautomaticcanningmachinesinafood-processingplant.
X
0
1
2
3
P(X)
0.35
0.35
0.25
0.05
Whatistheprobabilitythatthenumberofmachinefailuresis
a)exactlythree?
b)morethanone?
c)lessthantwo?
d)Calculatethemeanandvarianceofthenumberofmachinefailures.
Q.5Themaintenancedepartmentofacity'selectricpowercompanyfindsthatitiscostefficienttoreplaceallstreetlightbulbsatonce,ratherthantoreplacethebulbsindividuallyastheyburnout.Assumethatthelifetimeofabulbisnormallydistributedwithameanof3000hoursandastandarddeviationof200hours.Findtheprobabilitythatthelifetimeofabulbis
a)lessthan2750hours.b)between2900hoursand3350hrs.c)between2790hoursand2950hours.
b)Ifthedepartmentwantsnomorethan10%ofthebulbstoburnoutbeforetheyarereplaced,afterhowmanyhoursshouldallthebulbsbereplaced?
c)Ifthedepartmenttakesasampleof40streetlights,whatwouldbetheprobabilitythattheaveragelifetimeofthebulbswasmorethan3050hours?
Q.6Thefollowingtableshowsaconsumer’ssatisfactionwithfoodstores(X)inaparticulartownandY,thenumberofyearstheconsumerhasresidedinthattown.
X
Y
1
2
3
4
1
.04
.14
.23
.07
2
.07
.17
.23
.05
Whatistheprobabilitythat
(a)thenumberofyearsisequaltoone?
(b)Y=2andX=4?
(c)Y=1orX=3?
(d)thelevelofsatisfactionis3ifthenumberofyearsis2?
(e)FindthemarginaldistributionofX.
(f)WhatarethemeanandvarianceofX?
(g)FindtheconditionaldistributionofXgivenY=1.
(h)WhatarethemeanandvarianceofXgivenY=1.
(i)FindthecovarianceofXandY.
Q.8Thelifetimeofacertainbrandoftyresisapproximatelynormallydistributedwithameanof40000kmandastandarddeviationof2500km.Thetyrescarryawarrantyfor33000km.
a)Whatproportionofthetyreswillfailbeforethewarrantyexpires?
b)Whatproportionofthetyreswillfailafterthewarrantyexpiresbutbeforetheyhavelastedfor39000km?
c)Themanufacturerwishestosetthewarrantysuchthatthereisonlya2%failurerate.Whatnumberofkilometresmustheguarantee?
d)Whatistheprobabilitythattheaveragelifetimeof36tyresislessthan39500km?
e)Whatistheprobabilitythattheaveragelifetimeof23tyresismorethan40500km?
Q.9KeepKoolIncmanufactureswindowairconditionersinbothadeluxemodelandastandardmodel.AnauditorengagedinacomplianceauditofthefirmisvalidatingthesalesaccountforApril.Shehascollected200invoicesforthemonth,someofwhichweresenttowholesalersandtheremaindertoretailers.Theinformationisgiveninthetablebelow.
Wholesale
Retail
Deluxe
0.18
0.56
Standard
0.12
0.14
Iftheauditorselectsoneinvoiceatrandom,whatistheprobabilitythattheinvoiceselectedis
a)forthedeluxemodel.
b)forthedeluxemodelandaretailinvoice.
c)awholesaleinvoiceforthedeluxemodel.
d)aninvoiceforthestandardmodelorawholesaleinvoice
e)Aretheevents'retailinvoice'and'invoiceforastandardmodel'mutuallyexclusive?
f)Aretheevents'retailinvoice'and'invoiceforastandardmodel'independent
Q.10Thetablebelowshowsthetotalnumberofaccountingcoursesastudenttakes(X)andY,thesexofthestudent,where1denotesamalestudentand0afemalestudent.
X
Y
2
3
4
5
0
.14
.17
.08
.12
1
.16
.20
.12
.01
Whatistheprobabilitythatastudentselectedatrandom
a)ismale?
b)takes4accountingcoursesandisfemale?
c)takes5accountingcoursesorismale?
d)ismaleifhetakes2accountingcourses?
e)FindthemarginaldistributionofX.
f)WhatarethemeanandstandarddeviationofX?
g)WhatisthedistributionofXifthestudentisamale?
h)Whatarethemeanandvarianceofthedistributioninpart(g)?
i)ArethetwovariablesXandYindependent?
Givereasonsforyouranswer.
Q.11LetYrepresentthenumberoftimesahousewifevisitsasupermarketinaone-weekperiod.
Y
0
1
2
3
P(Y)
0.1
0.2
0.3
0.4
a)Findtheexpectedvalueandthestandarddeviationofthenumberofweeklyvisitstothesupermarket.
b)Whatistheprobabilitythatthehousewifevisitsthestore
i)atleastonce?
ii)nomorethantwice?
iii)exactlyonce?
Q.12LetXrepresentthenumberoftimesastudentvisitsanearbypizzaparlour.
X
0
1
2
3
P(X)
0.1
0.3
0.4
0.2
a)Calculatethemeanandstandarddeviationofthenumberofvisitstothepizzaparlour.
b)Whatistheprobabilitythatastudentvisitsthepizzaparlour
i)atmosttwice?
ii)atleasttwice?
iii)exactlyonce?
Q.13TherandomvariablesXandYhavemeansof10and16respectively,variancesof9and25respectivelyandthecovariancebetweenXandYequalto-4.
i)Findtheexpectedvalueandvarianceof2X-7.
ii)Findtheexpectedvalueandstandarddeviationof3X-4Y
iii)FindE(4-3X)andvar(4-3X)
iv)FindE(4-3X+2Y)andvar(4-3x+2Y)
Q.14Theheightsofboysofage15isnormallydistributedwithameanof150cmandastandarddeviationof20cm.Findtheprobabilitythattheheightofa15yearoldboyis
i)morethan155cms?
ii)between165cmand198cm?
iii)Whatheightmustthehighschoolbasketballteamsetsothatonlythetop10%ofboyswillbeeligibleforteamselection?
iv)IfIrandomlyselect18boys,whatistheprobabilitythattheiraverageheightsislessthan137cm?
Q.15Thedistributionofheartrateforpatientssufferingfromheartdiseaseisapproximatelynormalwithameanof97beatsperminuteandastandarddeviationof18.
a)Whatproportionofthesepeoplehaveheartbeats
i)below120?
ii)between100and115?
b)Ifarandomsampleof30peopleistaken,whatistheprobabilitythatthemeannumberofheartbeatsismorethan105beatsperminute?
Q.16Amanufacturerofcomputerchipsbelievesthatabout90%ofthecomputerchipsconformtospecifications.Ifhesamples100chips,whatistheprobabilitythatbetween82%and87%ofthecomputerchipsconformtospecifications?
Q.17ForthebivariateprobabilitydistributionofX,Ygivenbelow:
Y
X
1
2
0
0.1
0.25
1
0.2
0.15
2
0.25
0.05
a)CalculatethemarginaldistributionofX.
b)CalculatethemeanandstandarddeviationofX.
Whatistheprobabilitythat
c)Y=2andX=1?
d)X=1orY=2?
e)X=2ifY=1?
PART2
Q.1OverthepastfiveyearsthemeanageatdeathintheUnitedStateshasbeen70.5years.Inarandomsampleofthebiographiesof50‘famouspersons’whodiedinthisperiod,themeanageatdeathwas72.0yearswithastandarddeviationof6.3years.Dothesedatasuggestthatfamouspeopleontheaveragelivelongerthantherestofus?
Useasignificancelevelof0.05.
Q.2Inalargecity,22%ofthehouseholdshadtheafternoonpaperdeliveredtotheirdoors.Afterthenewspaperconductedanaggressivemarketingcampaigntoincreasethatfigure,arandomsampleof200householdswastaken.Ofthesamplegroup,61householdsnowhavethepaperdelivered.Canweconcludeatthe5%significancelevelthatthecampaignwasasuccess?
Findthep-valueofthetest.
Q.3Amanufactureroftelevisionpicturetubeshasaproductionlinethatproducesanaverageof100tubesperday.Becauseofnewgovernmentregulations,anewsafetydevicehasbeeninstalled,whichthemanufacturerbelieveswillreducetheaveragedailyoutput.Arandomsampleof15days'outputaftertheinstallationofthesafetydeviceisgiven
93103951019110596941018898941019295
Istheresufficientevidencetoconcludethattheaveragedailyoutputhasdecreasedfollowingtheinstallationofthesafetydevice.(Useα=0.05.)
Q.4Inanefforttoexplaintocustomerswhytheirelectricitybillshavebeensohighlatelyandhow,specifically,theycouldsavemoneybyreducingthermostatsettingsonbothspaceheatersandwaterheaters,anelectricitycompanyhascollectedtotalkilowattconsumption(inkilowatthours/100)figuresforlastyear’swintermonths,aswellasaveragethermostatsettingsonspaceheaters(indegreesCelsius)andaveragethermostatsettingsonwaterheaters(indegreesCelsius).
Modelfittingresultsfor:
Consumption
Independentvariablecoefficientstd.errort-valuesig.level
CONSTANT-51.5158.618-5.9780.0010
SpaceHeaters-0.7101.635-0.4340.6792
WaterHeaters1.6870.5732.9440.0258
R2=0.9586FStatistic69.5030
SumofSquaredResidual13.1397p-value0.0001
N=9
(i)Writetheestimatedequation,includingthestandarderrorsandR2.
(ii)Interpretthevalueofthecoefficientforspaceheaters.
(iii)Testthehypothesisthatthemodelisusefulforprediction.Useα=0.05.
(iv)Itisbelievedthattheslopeofthevariable,Waterheaters,is