Reading proficiency: An educator wants to construct a 99% confidence interval for the proportion of elementary school children in Colorado who are proficient In reading. Part 1 of 3 (a) The results of a recent statewide test suggested that the proportion is 0.71. Using this estimate, what sample size is needed so that the confidence interval will have a margin of error of 0.077 A sample of 279 elementary school children is needed to obtain a 99% confidence interval with a margin of error of 0.07 Part: 1/3 Part 2 of 3 (b) Estimate the sample size needed if no estimate of P is available. A sample of 340 elementary school children is needed to obtain a 99% confidence interval with a margin of error of 0.07,