怎样才能从DOE中得到回归方程

我在用MITAB进行DOE分析时,当完成STAT-DOE-Factorial-Analze factorial design后,可以得一个总,如下:
Factorial Fit: strength versus A, B, C

Estimated Effects and Coefficients for strength (coded units)

Term Effect Coef SE Coef T P
Constant 66.325 2.205 30.08 0.000
A -17.800 -8.900 2.205 -4.04 0.016
B 21.700 10.850 2.205 4.92 0.008
C -2.200 -1.100 2.205 -0.50 0.644
A*B -11.750 -5.875 2.205 -2.66 0.046
A*C -1.750 -0.875 2.205 -0.40 0.712
B*C 3.950 1.975 2.205 0.90 0.421
Ct Pt -0.800 3.819 -0.21 0.844


S = 6.23634 R-Sq = 92.43% R-Sq(adj) = 79.19%


Analysis of Variance for strength (coded units)

Source DF Seq SS Adj SS Adj MS F P
Main Effects 3 1585.14 1585.14 528.380 13.59 0.015
2-Way Interactions 3 313.45 313.45 104.485 2.69 0.182
Curvature 1 1.71 1.71 1.707 0.04 0.844
Residual Error 4 155.57 155.57 38.892
Lack of Fit 1 9.68 9.68 9.680 0.20 0.686
Pure Error 3 145.89 145.89 48.629
Total 11 2055.87
当删除C,AC,BC后,再进行一次运算,也得不出回归方程, 请教高手,怎样才能得到回归方程,而书也没有说清楚,只告诉我们自已可以根据总表写出回归方程,我在MINITAB的设定中,哪里出错了?