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Confidence Interval and Sample Size

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Suppose we want to conduct a poll to estimate the proportion of voters who favor the new healthcare bill, and we plan to use a 95% confidence interval for our estimate. Determine the sample size needed so that the sample proportion is within a margin of error of 0.03 of the true proportion of all voters who are in favor of the bill.

You will have to assume in your computation that 50% of the electorate could be in favor of the bill.

Sample Size =

Round your answer to the nearest whole number.

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Anwesha Ghosh, MSc
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  • MSc, Osmania University
  • MSc, Indian Institute of Technology - Roorkee (I.I.T.-ROORKEE)
  • BSc, Banaras Hindu University
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