How's the economy? A polister wants to construct an 80% confidence interval for the proportion of adults who believe that economic conditions are getting better.
Part 1 of 2
(a) A poll taken in July 2010 estimates this proportion to be 0.41. Using this estimate, what sample size is needed so that the confidence interval will have
a margin of error of 0.01?
A sample of 3976 adults is needed to obtain an 80% confidence interval with a margin of error of 0.01.
Part: 1/2
Part 2 of 2
(b) Estimate the sample size needed if no estimate of p is available.
A sample of adults is needed to obtain an 80% confidence interval with a margin of error of 0.01.
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