Table 5.

Variation analysis of Box–Behnken design quadratic model.

Source of Variation	Mean Square	Degree of Freedom	Sum of Square	p-Value
Model	378.24	9	42.03	<0.0001 **
X 1	204.83	1	204.83	<0.0001 **
X 2	20.70	1	20.70	0.0044 **
X 3	113.63	1	113.63	<0.0001 **
X 1 X 2	1.82	1	1.82	0.2596
X 1 X 3	29.27	1	29.27	0.0017 **
X 2 X 3	3.71	1	3.71	0.1237
X 1 2	0.70	1	0.70	0.4709
X 2 2	0.03	1	0.03	0.8839
X32	3.31	1	3.31	0.1424
Residual	8.48	7	1.21
Lack of fit	5.89	3	1.96	0.1562
Pure error	2.59	4	0.65
Sum	386.72	16	42.03

Note: ** indicates extremely significant (p < 0.01).