进一步比较平均偏离平均值的程度 Ch4-50 甲一[2×(10-83)+(9-83)+(8-8.3) +(7-8.3)2+(6-8.3)2] 1334/6=222∑( E(XPK k=1 乙[(10-8.3)2+(9-8.3)2 EIX-E(X12 +3×(8-83)2+(7-8.3)2] =534/6=089今∑(x-E(X) k=1Ch4-50 进一步比较平均偏离平均值的程度 甲 (7 8.3) (6 8.3) ] [2 (10 8.3) (9 8.3) (8 8.3) 6 1 2 2 2 2 2 + − + −  − + − + − 乙 3 (8 8.3) (7 8.3) ] [(10 8.3) (9 8.3) 6 1 2 2 2 2 +  − + − − + − =13.34/ 6 = 2.22 = 5.34/ 6 = 0.89 ( ) = − 5 1 2 ( ) k k k x E X p ( ) = − 4 1 2 ( ) k k k x E X p E [X - E(X)]2