Table 2.

Variance analysis of items in regression equation.

Sources of Variation	Sum of Squares	df	Mean Square	F Value	p Value	Significance
model	23.90	9	2.66	41.57	<0.0001	***
X1	1.93	1	1.93	30.23	0.0009	***
X2	1.34	1	1.34	21.06	0.0025	**
X3	0.66	1	0.66	10.26	0.0150	*
X1X2	1.36	1	1.36	21.25	0.0025	**
X1X3	4.45	1	4.45	69.71	<0.0001	***
X2X3	0.20	1	0.20	3.10	0.1217
X12	10.48	1	10.48	164.06	<0.0001	***
X22	0.99	1	0.99	15.51	0.0056	**
X32	1.48	1	1.48	23.14	0.0019	**
residual	0.45	7	0.064
lack of fit	0.21	3	0.071	1.23	0.4096	no
pure error	0.23	4	0.058
total	24.34	16
R2	0.9816
Radj2	0.9580
Adeq precision	17.696

* p < 0.05; ** p < 0.01; *** p < 0.001.