What proportion of Americans get most of their news from the Internet? According to a poll conducted by Pew Research Center, 40% get most of their news from the Internet. (Data extracted from "Drill Down," The New York Times, January 5, 2009, p. B3.)
a. To conduct a follow-up study that would provide 95% confidence that the point estimate is correct to within ± 0.04 of the population proportion, how large a sample size is required?
b. To conduct a follow-up study that would provide 99% confidence that the point estimate is correct to within ± 0.04 of the population proportion, how many people need to be sampled?
c. To conduct a follow-up study that would provide 95% confidence that the point estimate is correct to within ± 0.02 of the population proportion, how large a sample size is required?
d. To conduct a follow-up study that would provide 99% confidence that the point estimate is correct to within ± 0.02 of the population proportion, how many people need to be sampled?
e. Discuss the effects on sample size requirements of changing the desired confidence level and the acceptable sampling error.