Table 5 Model coefficient estimated by linear regression (R ² = 0.968, adjusted R ² = 0.937)

Intercept

97.168

3.605

26.950

0.000

X ^a₁

−5.552

1.693

−3.279

0.013

X ^b₂

7.729

1.693

4.565

0.003

X ^c₃

−8.043

1.693

−4.750

0.002

X ²₁

2.765

2.212

1.249

0.251

X ²₂

−0.922

2.212

−0.417

0.689

X ²₃

0.185

2.212

0.083

0.935

X₁X₂

−15.022

1.863

−8.061

0.000

X₁X₃

−18.153

1.863

−9.741

0.000

X₂X₃

−17.997

1.863

−9.657

0.000