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Final

STA 205 Lecture Notes - Lecture 10: Confidence IntervalExam


Department
Statistics
Course Code
STA 205
Professor
Brooke Buckley
Study Guide
Final

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12/17/2018 NKU Imath Assessment
https://imath.nku.edu/course/gb-viewasid.php?stu=11461&cid=335&asid=153573&uid=11461 1/8
Grade Book Detail
Damico , Emily
Topic 10: Confidence Interval for the Mean
Started: November 8, 2018, 1:51 pm
Last change: November 8, 2018, 3:44 pm
Time spent: 112 minutes
Total time questions were on‑screen: 72.1 minutes.
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Anarticleinvestigatedtheconsumptionofcaffeineamongwomen.Asampleof42womenwereaskedto
monitortheircaffeineintakeoverthecourseofoneday.Themeanamountofcaffeineconsumedinthe
sampleofwomenwas238.159mgwithastandarddeviationof203.245mg.Inthearticle,researcherswould
liketoincludea98%confidenceinterval.
Thevaluesbelowaretcriticalpointcorrespondingto90%,95%,98%,and99%confidence.Which
criticalpointcorrespondsto98%confidence?
2.02
2.421
2.701
1.683
With98%confidence,weestimatethemeanamountofcaffeineconsumedbywomenisbetween
mgand mg.(Roundthelimitsofyourintervalto4decimalplaces.)
Ifthelevelofconfidencewerechangedto90%,whateffectwouldthishaveonthewidthofthe
calculatedconfidenceinterval?
theintervalwouldnarrow
theintervalwouldwiden
therewouldbenoeffectontheinterval
Answer:2.421
Answer:162.233
Answer:314.085
Answer:theintervalwouldnarrow
Question 1: 8 (parts: 1.5, 2.5, 2.5, 1.5) out of 8 (parts: 1.5, 2.5, 2.5, 1.5)in 2 attempt(s)

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12/17/2018 NKU Imath Assessment
https://imath.nku.edu/course/gb-viewasid.php?stu=11461&cid=335&asid=153573&uid=11461 2/8
ArecentarticlepublishedbytheWallStreetJournalsaidtheCincinnatiairporthadthemostexpensive
airfaresamongthelargestairportsintheUS.Whiletheyhadsomestatisticstosupportthisstatement,a
statisticiandecidedtoinvestigatefurther.Asampleof46flightsoriginatinginCincinnatiwasselected,and
theroundtripairfareforeachflightwasrecorded.ThesampledataissummarizedintheStatCrunchoutput
below:
With95%confidence,weestimatethemeanairfareforflightsoutofCincinnatiisbetween$
and$ .(Roundthelimitsofyourintervalto4decimalplaces.)
Themeanairfarenationwidewasreportedas$376foraroundtripticket.Doestheintervalfound
abovesupporttheclaimthatCincinnatihasairfareswhicharemoreexpensivethanotherairportsin
theUS?
Theintervaldoesnotsupportthisclaimbecauseanairfareof$376doesnotfallinsidethe
interval.
Theintervaldoesnotsupporttheclaimbecausetheentireintervalisnotabove$376.
Theintervalsupportstheclaimbecausetheentireintervalisgreaterthan$376.
Wecan'tmakethisconclusionbasedonaconfidenceinterval.
Youneedtoscheduleaflightforthesummer.Ifyouwanttoestimatethecostofyourflight,which
intervalwouldbemostappropriateforestimatingthecost?
theconfidenceinterval
anintervalbasedontheEmpiricalRuleorChebyshev'sRule(dependingontheshapeofthe
data)
Supposethesampleselectedwastakensothatthe46mostexpensiveflightsfromCVGwereselected.
Whichassumptionhasbeenviolated?
quantitativedata
randomsample
normality
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12/17/2018 NKU Imath Assessment
https://imath.nku.edu/course/gb-viewasid.php?stu=11461&cid=335&asid=153573&uid=11461 3/8
Answer:426.5934
Answer:501.7169
Answer:Theintervalsupportstheclaimbecausetheentireintervalisgreaterthan$376.
Answer:anintervalbasedontheEmpiricalRuleorChebyshev'sRule(dependingontheshapeofthedata)
Answer:randomsample
Question 2: 8 (parts: 2.5, 2.5, 1, 1, 1) out of 8 (parts: 2.5, 2.5, 1, 1, 1)in 1 attempt(s)
TheCleaningInstituteconductedasurveyin2009of819adultsaskingeachadultthenumberoftimesthey
washtheirhandsperday.Themeannumberoftimesthosesampledwashedtheirhandswas8.908witha
standarddeviationof5.245.Researcherswouldliketoincludea90%confidenceinterval.
Howmanydegreesoffreedomwouldbeassociatedwiththetdistribution?df=
With90%confidence,weestimatethemeannumberoftimesanindividualwashestheirhandsis
between and .(Theappropriatetcriticalpointist=1.647.Roundthelimitsofyour
intervalto4decimalplaces.)
Basedontheintervalcomputed,canweconcludethetypicalAmericanadultwashestheirhandsfewer
than9timesperday,onaverage?
Yes.Theintervalfallsentirelybelow9.
No.Theintervalextendsabove9.
Yes.Mostoftheintervalfallsbelow9.
Answer:818
Answer:8.606
Answer:9.21
Answer:No.Theintervalextendsabove9.
Question 3: 6 (parts: 1, 2.5, 2.5, 0) out of 8 (parts: 1, 2.5, 2.5, 2)in 3 attempt(s)
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