S1 S2Fa2(n1-1,n2-1)S2Fa2(n1-1,n2-1) 这里a=0.10,a/2=0.05,1-∞/2=0.95, n1=18,s1=0.34,2=13,2=0.29F(17,12)=259, F(17,12)=Fs(12,17)238 故两总体方差比a/02的置信水平为0.90的置信区 间为 (0.45,2.79)这里 α = = − = 0.10, 2 0.05,1 2 0.95, α α F0.05 (17,12) 2.59, = (0.45 , 2.79) . 2 2 1 1 2 2 n s n s = = = = 18, 0.34, 13, 0.29. 0.95 0.05 1 1 (17,12) . (12,17) 2.38 F F = = 故两总体方差比 的置信水平为0.90 的置信区 间为 2 2 1 2 σ σ         − − − ( −1, −1) , ( 1, 1) 1 2 1 2 2 2 2 1 2 1 2 2 2 2 1 S F n n S S F n n S a a