Question

In May 2012, a Gallup Poll showed that 63% of randomly surveyed U.S. adults said the United States benefits from having a rich class. (The proportion was unchanged from 1990. The percentage was higher for Republicans than for Democrats.)
a. Assuming the sample size was 500, how many would have said that the United States benefits from having a rich class?
b. Is the sample size large enough to apply the Central Limit Theorem? Explain. Assume the other conditions for using the CLT are met.
c. Find a 95% confidence interval for the percent that believe the United States benefits from having a rich class, using the numbers from part a.
d. Find the width of the interval you found in part c by subtracting the lower boundary from the upper boundary.
e. Now assuming the sample size was multiplied by 9 (n = 4500) and the percentage was still 63%, how many would have said the United States benefits from having a rich class?
f. Find a 95% confidence interval, using the numbers from part e.
g. What is the width of the interval you found in part f?
h. When the sample size is multiplied by 9, is the width of the interval divided by 9? If not, what is it divided by?


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  • CreatedJuly 16, 2015
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