1
Economic Statistics
Econ 321
Homework 4:
due Tuesday June 15
Solve the following problems. Explain your logic and show your steps.
1.
A survey of 100 students found that they spend on average 100 minutes every week in sport related activities
with a standard deviation of 50 minutes.
a.
Find the 95% confidence interval for the population mean.
b.
Find the 90% confidence interval for the population mean. Is it wider or narrower? Explain.
c.
If the sample of students surveyed was only 64, how would the 90% confidence interval for the
population mean change? Explain.
2.
A national survey of 1,900 persons found that 45% would vote for a Republican candidate in the next election.
a.
With a 99% confidence in what range will the number of Republican voters in the next election be given
that the US has 170 million registered voters?
b.
If the size of the survey was increased to 2,500 could you be more precise on your estimate for the
number of Republican voters in the next election? Explain. What would be the new 95% interval?
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 Spring '11
 chugh
 Statistics, Standard Deviation, Georgetown University

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