Estimated regression coefficients for the quadratic polynomial model and the analysis of variance (ANOVA) for the experimental results^a.

Parameter	Coefficient estimate	Standard error	Sum of squares	DF	Mean square	F value
Model			37.53	9	4.17	251.40***
Intercept	16.85	0.058		1
X 1	0.26	0.046	0.55	1	0.55	32.92***
X 2	0.78	0.046	4.82	1	4.82	290.63***
X 3	1.65	0.046	21.65	1	21.65	1305.18***
X 1 X 2	2.500 × 10−3	0.064	2.500 × 10−5	1	2.500 × 10−5	1.507 × 10−3NS
X 1 X 3	−0.13	0.064	0.068	1	0.068	4.08NS
X 2 X 3	−0.21	0.064	0.18	1	0.18	10.64*
X 1 2	−0.43	0.063	0.78	1	0.78	46.88***
X 2 2	−0.90	0.063	3.45	1	3.45	207.80***
X 3 2	−1.10	0.063	5.12	1	5.12	308.42***
Residual			0.12	7	0.017
Lack of fit			0.091	3	0.030	4.89NS
Pure error			0.025	4	6.320 × 10−3
R 2	0.9969		Adj R2	0.9930
CV%	0.82		Pred R2	0.9603
Press	1.49		Adeq. precision	49.430

^a*P < 0.05, **P < 0.01, ***P < 0.001, NS – not significant.