Table 3 Analysis of variance (ANOVA) results for the equation using Design-Expert 10

Model

14

2499.53

178.54

68.38

<0.0001*

X ₁

1

793.50

793.50

303.89

<0.0001*

X ₂

1

8.17

8.17

3.13

0.0973

X ₃

1

170.67

170.67

65.36

<0.0001*

X ₄

1

150.00

150.00

57.45

<0.0001*

X ²₁

1

1226.68

1226.68

469.79

<0.0001*

X ²₂

1

56.68

56.68

21.71

0.0003*

X ²₃

1

24.11

24.11

9.23

0.0083*

X ²₄

1

78.11

78.11

29.91

<0.0001*

X ₁ X ₂

1

56.25

56.25

21.54

0.0003*

X ₁ X ₃

1

36.00

36.00

13.79

0.0021

X ₁ X ₄

1

1.00

1.00

0.38

0.5453

X ₂ X ₃

1

9.00

9.00

3.45

0.0831

X ₂ X ₄

1

16.00

16.00

6.13

0.0257

X ₃ X ₄

1

12.25

12.25

4.69

0.0468

Residual

15

39.17

2.61

Lack of fit

10

33.67

3.37

3.06

0.1144

Pure error

5

5.50

1.10

Cor. total

29

2538.70