求高手解答黑带考试教材p330疑问

黑带考试教材p330全因子分析中,方差分析表中lack of fit消失掉了,合并到pure error项中,这是为什么?

Results for: 马林黑带教材全因子P325.MTW

Factorial Fit: y versus A, B

Estimated Effects and Coefficients for y (coded units)

Term Effect Coef SE Coef T P
Constant 66.042 1.449 45.59 0.000
A -17.800 -8.900 1.774 -5.02 0.001
B 21.700 10.850 1.774 6.12 0.000
A*B -11.750 -5.875 1.774 -3.31 0.011


S = 5.01777 R-Sq = 90.19% R-Sq(adj) = 86.51%


Analysis of Variance for y (coded units)

Source DF Seq SS Adj SS Adj MS F P
Main Effects 2 1575.46 1575.46 787.730 31.29 0.000
2-Way Interactions 1 276.13 276.13 276.125 10.97 0.011
Residual Error 8 201.42 201.42 25.178
Curvature 1 1.93 1.93 1.927 0.07 0.802
Pure Error 7 199.50 199.50 28.500
Total 11 2053.01