On May 23, 2013, Gallup reported that of the 1,005 people surveyed, 76% of U.S.

Question

On May 23, 2013, Gallup reported that of the 1,005 people surveyed, 76% of U.S. workers believe that they will continue working past retirement age. The confidence level for this study was reported at 95% with a +-3% margin of error.

a. Determine the estimated proportion from the sample.

b. Determine the sample size

c. Identify CL and .

d. Calculate the error bound based on the information provided.

e. Compare the error bound in part d to the margin of error reported by Gallup. Explain any differences between the values.

f. Create a confidence interval for the results of this study.

g. A reporter is covering the release of this study for a local news station. How should she explain the confidence interval to her audience?

Explanation / Answer

a. Estimated proportion is 0.76

b. Sample size is n=1005

c. CL=95% and alpha=1-95/100=0.05

d. Margin of error=z*sqrt(p(1-p)/n)=1.96sqrt(0.76*0.24/1005)=0.01

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