In a certain region, 25% of people over age 50 didn't graduate from high school. We would like to know if this percentage is the same among the 25-30 year age group (a) How many 25-30 year old people should be surveyed in order to estimate the proportion of non-grads to hin 4%, with 8%, confidence?
(b) Suppose we wanted to cut the margin of error to 3%. How many people should be sampled now?
(c) what sample size is required for a margin of error of 8%?