Reading prociency: An educator wants to construct a 95% condence interval for the proportion of elementary school children in Colorado who are procient in reading. (a) The results of a recent statewide test suggested that the proportion is 0.68. Using this estimate, what sample size is needed so that the condence interval will have a margin of enor of 0.05? A sample of E] elementary school children is needed to obtain a 95% condence interval with a margin of error of 0.05