Political science, inc. (psi) specializes in voter polls and surveys designed to keep political office seekers informed of their position in a race. using telephone surveys, interviewers ask registered voters who they would vote for if the election were held that day. in a recent election campaign, psi found that 220 registered voters, out of 500 contacted, favored a particular candidate. develop a 95% confidence interval estimate for the proportion of the population of registered voters that favors the candidate.