The Centers for Disease Control reported the percentage of people 18 years of age and older who smoke (CDC website, December 14, 2014). Suppose that a study designed to collect new data on smokers and nonsmokers uses a preliminary estimate of the proportion who smoke of .30.
a. How large a sample should be taken to estimate the proportion of smokers in the population with a margin of error of .02 (to the nearest whole number)? Use 95% confidence.
b. Assume that the study uses your sample size recommendation in part (a) and finds 520 smokers. What is the point estimate of the proportion of smokers in the population (to 4 decimals)?
c. What is the 95% confidence interval for the proportion of smokers in the population (to 4 decimals)?
( , )
In order to solve this problem, part a is necessary to lead to the answers in the following problems. So I don't want to worry about problem b and c until I have a figured out. What I have so far is that to find a sample size, I should set up the equation as such:
[(1.96)^2(#)^2]/(.02)^2. I could easily solve this problem but I just don't know how to solve for the missing value.
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