Table 6.

The t- and p- values of the reduced model with X1, X2, X3 as independent variables

Parameter	t-value	p-value
Intercept	15.56	<0.0001
X1	−2.81	0.0076
X2	1.54	0.132
X3	3.1	0.0036
X1 × X1	0.66	0.5123
X2 × X1	−2.11	0.0407
X2 × X2	−2.69	0.0105
X3 × X1	−0.28	0.7835
X3 × X2	−0.1	0.9199
X3 × X3	−2.88	0.0064
Linear		0.001
Quadratic		0.0035
Cross product		0.2242

R² = 0.5022 for the reduced model