Table 3. Analysis of variance for the second-order model

Model terms: X1, X2, X3; X12, X22, X32; X1X2, X1X3, X2X3
Source	Degrees of freedom	Sum of squares	Mean square	F-value	p-value
Model	9	1187.5291	131.9477	3.31	0.0642
Error	7	278.8277	39.8325	-	-
Total	16	1466.3568	-	-	-
Root MSE = 6.3113		R-square = 0.8099		Adjusted R-square = 0.5654
Test of lack of fit
Source	Degrees of freedom	Sum of squares	Mean square	F-value	p-value
Lack of fit	5	272.8623	54.5725	18.3	0.0526
Pure Error	2	5.9654	2.9827	-	-