Table 4. Analysis of variance for a third-order model on Y₁

Source	DF	Sum of squares	Mean square	F-value	Pr>F-value
Model	18	2,672.0946	148.4497	23.91	<0.0001
Error	8	49.6617	6.2077
Lack of fit	6	44.5350	7.4225	2.90	0.2788
Pure error	2	5.1267	2.5633
Corrected total	26	2,721.7563
Root MSE=2.49153, Dependent mean=79.32963, r2=0.9818, Adj r2=0.9407

Model terms: X₁, X₂, X₃, X₄; X₁², X₂², X₃², X₄²; X₁X₂, X₁X₃, X₁X₄, X₂X₃, X₂X₄, X₃X₄ X₁³, X₂³, X₃³, X₄³.