xii X~N(4,c2）i=1,2,,a;j=1,2,,n E≈N0,σ2) Level Ar A2 Aa Observations X11 X21 Xal 2 Xaj XInl X2n2 Xana Population 41 42 a meanLevel A1 A2 ··· Aa Observations x11 x21 ··· xa1 x1j x2j ··· xaj x1n1 x2n2 ··· xana Population mean 1 2 a Xi ～N( i,  2 ) xij = i + ij i = 1, 2,···, a；j = 1, 2,···, ni ij ～ N(0, 2 )