intro to statistics fall 2017 – midterm name
TRANSCRIPT
1. True/FalseQuestions–Iffalse,stateyourreasonwhyormakeitatruestatement.
a. Aprobabilityof0.1indicatesanunusualevent.�
b. Whenaneventisalmostcertaintohappen,itscomplementwillbeanunusual
event.
c. Whentwoeventsaremutuallyexclusive,theyhavenooutcomesincommon.
d. Whentwoeventsareindependent,theyarealsomutuallyexclusive.�
e. Acombinationisanorderedarrangementofobjects.�
f. Thenumberofdifferentorderedarrangementsofndistinctobjectsisn!
g. Themeanoftherandomvariableofaprobabilitydistributiondescribeshowthe
outcomesvary.�
h. Theexpectedvalueofarandomvariablecanneverbenegative.
i. Thevarianceofarandomvariablecanneverbenegative.
j. Anexperimentisaprocesswhoseoutcomecanbepredictedwithcertainty.
2. Usethetable,whichshowstheapproximatedistributionofthesizesoffirmsforarecentyear.
a. Findtheprobabilitythatarandomlyselectedfirmwillhaveatleast10employees.
b. Findtheprobabilitythatarandomlyselectedfirmwillhavefewerthan20employees.
3. Acardisrandomlyselectedfromastandarddeckof52playingcards.Findtheprobabilitythatthecardisredoraqueen.
4. Abatchof200calculatorscontains3defectiveunits.Whatistheprobabilitythatasampleofthreecalculatorswillhave(a)nodefectivecalculators?(b)alldefectivecalculators?(c)atleastonedefectivecalculator?(d)atleastonenon-defectivecalculator?
5. Findthea. meanb. variancec. standarddeviationoftheprobabilitydistributiond. interprettheresults.
Thenumberofcellphonesperhouseholdinasmalltown.
6. Findtheindicatedbinomialprobabilities.Thirty-fourpercentofU.S.adultspersonallyownagun.Yourandomlyselect12U.S.adults.FindtheprobabilitythatthenumberofU.S.adultswhosaytheypersonallyownagunis(a)exactlytwo(b)atleasttwo(c)morethantwo.
7. Twenty-twopercentofformersmokerssaytheytriedtoquitfourormoretimesbeforetheywerehabit-free.Yourandomlyselect10formersmokers.Findtheprobabilitythatthefirstpersonwhotriedtoquitfourormoretimesis(a)thethirdpersonselected(b)thefourthorfifthpersonselected(c)notoneofthefirstsevenpeopleselected.