In a poll conducted by the Nanos Research on May 1, 2011, 38.7% of n = 702 decided voters supported the Conservative.
(a) Find a 95% confidence interval for p, the proportion supporting the Conservative. What is the margin of error?
(b) If we need an estimate of a proportion to be within 0.037 (i.e., 3.7%) at the level of confidence 95% (i.e., 19 times out of 20), how large should the sample size be?