Table 3. ANOVA for the Quadratic Model^a.

source	sum of squares	df	mean square	F-value	prob > F
model	10753.51	9	1194.83	247.10	<0.0001	significant
X1-first cross-linking	7793.14	1	7793.14	1611.66	<0.0001
X2-imprinting pH	427.49	1	427.49	88.41	<0.0001
X3-second cross-linking	232.52	1	232.52	48.09	0.0002
X1X2	300.68	1	300.68	62.18	<0.0001
X1X3	253.29	1	253.29	52.38	0.0002
X2X3	62.57	1	62.57	12.94	0.0088
X12	1465.65	1	1465.65	303.10	<0.0001
X22	143.10	1	143.10	29.59	0.0010
X32	3.66	1	3.66	0.76	0.4132
residual	33.85	7	4.84
lack of fit	25.64	3	8.55	4.16	0.1010	not significant
pure error	8.21	4	2.05
Cor total	10,787.35	16

^aR² = 0.996, pred. R² = 0.961, adj. R² = 0.993.