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Table 4 The coefficient estimates and significance of the response surface model

From: A novel design for biodiesel production from methanol + mutton bone fat mixture

Factor

Coefficient estimate

Standard error

95% CI low

95% CI high

VIF

Intercept

79.41

1.36

76.41

82.40

 

X1

− 0.16

0.66

− 1.61

1.28

1

X2

− 0.68

0.66

− 2.13

0.77

1

X3

1.59

0.72

0.0062

3.18

1

X21

− 1.33

0.56

− 2.56

− 0.095

1.3

X22

− 2.12

0.56

− 3.35

0.89

1.3

X1X2

1.56

1.14

− 0.95

4.06

1

X1X3

5.63

0.66

4.18

7.07

1

X2X3

6.19

0.66

4.74

7.64

1