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Statistics & Pronabinty  Test #4 (Ci ape: 18 and Confidence LEICSXV’ﬂle
ow All World 31 A state’s Department of Education reports that 12% of the high school students in that stste
attend private high schools. The State University wonders if the percentage is the same in their
applicant pool. Admissions officers plan to check a random sample of the over 10,000 applications
on file to estimate the percentage of students applying for admission who attend private schools.
a. They actually select a random sample of 450 applications, and find that 46 of those students
attend rivate schools. Create thevconfidence interval. I8;
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70492 e 5.02%; x. .o a o. b. interpret the confidence interval this context $56,805
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C. if We increased the confidence level. would the Margin of Error increase or decrease Please explain your answer. It? in? it:£%<’0.£§'d ﬁn?)
Noon: :mt‘rf‘ 3:949 Q Mira/Qt" nei'nli}eri/ ) .t‘ wi gr S’S'f‘ Q. Should the admissions officers conclude that the p reentage of private school students in
their applicant pool is lower ti an the statewide enrollment rate of 12%? Explain Call” (Duct4&2, {ﬁat7 lit£1 .30 +14% ’” g; «+6’MITQLQ,
M is": 376 i’WW‘ eiieved that nearsightedHess affects abou: 12% of children. A school district gives
3 incoming kindergarten ckildren a EX: lain Why a Normal model can be used to describe the sampling a" ii," ., '3. Find the mean an C. Sketch and clear/1&1abeiri‘he—modeiwiisﬂigg the 6895—99] Ruie  p over 15% of {he ch iidren wiii be found to be . 4"“!
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“L 4.23/13 3. Wildlife scientists stud 1:10 21 certain s ecies of freos know that as: records indicate the adi‘lts
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Should wewh c, an average of ME grams with a standard deviation of 14 grams. The researchers
collect a random sample of 50 adult frogs and we igh them. in their sample the mean weight was
only 110 grams.
a. Explam why a l Tormal model can be used to describe the sampling distribution for the
sample mean. 7. g, .. , 7 7 . 117' 3‘5.)
"\ x SALHT 6“ >3" b. Find the mean and the standard deviation of {he trigdel
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Cl. One of the sczentxsts IS alarme 7 fearing that enmro ntal ‘C‘idnges may be adversely affecting the frogs. Do you :hink this sample result is unusually low? Explain. A 3" ‘7 4s A professor at a large university believes that students take an average of 15 credit hours per term. A random sample of 24 students in her class of 250 students had a mean of 16.6 credit hours
and a standard deviation of 2.22 credit hours. 3. Find a 95% confidence interval for t
professor’s class. c. Does this confidence interval indicate that students are taking more credit hours than the
professor believes? Explain your answer. o ...
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This note was uploaded on 04/12/2011 for the course STA 215 taught by Professor Tba during the Spring '08 term at Grand Valley State.
 Spring '08
 TBA

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