There are many reasons adults use credit cards. A recent survey ("Why Adults Use Credit Cards," USA Today, October 18, 2007, p. 1D) found that 66% of adults used credit cards for convenience.
a. To conduct a follow-up study that would provide 99% confidence that the point estimate is correct to within ± 0. 03 of the population proportion, how many people need to be sampled?
b. To conduct a follow-up study that would provide 99% confidence that the point estimate is correct to within ±0.05 of the population proportion, how many people need to be sampled?
c. Compare the results of (a) and (b).