l Confidence Interval: u, o Known where x= sample mean ASSUMPTION: o=population standard infinite population deviation n= sample size z= standard normal score for area in tail=a/2 /2 O/2 z x+z o 2002 The Wadsworth GroupConfidence Interval: µ, s Known where = sample mean ASSUMPTION: s = population standard infinite population deviation n = sample size z = standard normal score for area in tail = a/2 a 2 −a a 2 n x x z n x x z z z z s ×s × + + : – : – 0 x © 2002 The Wadsworth Group