ANOVA results for quadratic model^a.

Source	Sum of squares	Degree of freedom	Mean square	F-value	p-value
Model	2803.40	14	200.24	33.54	<0.0001
X 1	3.64	1	3.64	0.6105	0.4547
X 2	97.53	1	97.53	16.33	0.0029
X 3	10.28	1	10.28	1.72	0.2220
X 4	1.28	1	1.28	0.2144	0.6544
X 1 X 2	5.29	1	5.29	0.8860	0.3711
X 1 X 3	0.5625	1	0.5625	0.0942	0.7659
X 1 X 4	7.29	1	7.29	1.22	0.2978
X 2 X 3	1.56	1	1.56	0.2617	0.6213
X 2 X 4	4.84	1	4.84	0.8106	0.3914
X 3 X 4	2.40	1	2.40	0.4024	0.5417
X 1 2	41.27	1	41.27	6.91	0.0274
X 2 2	1118.53	1	1118.53	187.33	<0.0001
X 3 2	2.57	1	2.57	0.4302	0.5283
X 4 2	13.27	1	13.27	2.22	0.1702
Residual	53.74	9	5.97
Cor total	2857.13	23

^a R ² = 0.9812; adjusted R² = 0.9519; predicted R² = 0.8683.