Suppose the U.S. president wants to estimate the proportion of the population that supports his current policy toward revisions in the health care system. The president wants the margin of error to be 0.04. Assume a 95% level of confidence. The president’s political advisors found a similar survey from 2 years ago that reported that 60% of people supported health care revisions.

a. How large of a sample is required?

b. How large of a sample would be necessary if no estimate were available for the proportion supporting current policy?