We have k groups of observations. Each group has n, observations, that is, Ya, Yz, Yin , 1 Sisk. Let Y, denote the sample mean of the group : while Y is the grand mean. Let N = M 1. (2 pts) Show that a. where wi = n,/N. Remark. Consider k = 2. Then, 12 Y = = ni + 12 m + n2 b. (2 pts) Show that if m = .. = nx = n, then Remark. Consider & = 2. Then, - i+ 2- 0.58 + 0.582. 2