suppose the u.s. president wants an estimate of the proportion of the population who support his current policy toward revisions in the health care system. the president wants the estimate to be within .04 of the true proportion. assume a 95% level of confidence. the presidents political advisors estimated the proportion supporting the current policy to be .60. 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?