Level of Confidence 1 x 100 90 95 99 Area in Each Tail 0 05 0 025 0 005 a 2 Critical Value Z 2 1 645 1 96 2 575 People were polled on how many books they read the previous year Initial survey results indicate that s 11 7 books a How many subjects are needed to estimate the mean number of books read the previous year within four books with 95 confidence This 95 confidence level requires enter your response here Round up to the nearest subject