please explain

How's the economy? A pollster wants to construct a 99.8% confidence interval for the proportion of adults who believe that economic conditions are getting better. Part 1 of 2 X (a) A poll taken in July 2010 estimates this proportion to be 0.27. 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 18821.74 adults is needed to obtain a 99.8% confidence interval with a margin of error of 0.01. Correct Answer: 18820 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 a 99.8% confidence interval with a margin of error of 0.01