Hi Generally when p is unknown, p = .5 is used 99% confident, z = 2.576 ME = .02 n == = 4147.36 Always round Up: n = 4148 Sample size = CI z = value 90% z =1.645 92% z = 1.751 95% z = 1.96 98% z = 2.326 99% z = 2.576 Wish You the Best in your Studies.