Source of variation

Quadratic sum

Degree of freedom

Variance

F value

Prob > F

Significance

Model

575.76

14

41.13

23.49

<0.0001

^**

X1

113.34

1

113.34

64.75

<0.0001

^**

X2

3.91

1

3.91

2.23

0.1572

X3

136.82

1

136.82

78.16

<0.0001

^**

X4

4.19

1

4.19

2.39

0.1442

X1X2

1.51

1

1.51

0.86

0.3683

X1X3

10.50

1

10.50

6.00

0.0281

^*

X1X4

26.83

1

26.83

15.33

0.0016

^**

X2X3

17.68

1

17.68

10.10

0.0067

^**

X2X4

7.73

1

7.73

4.41

0.0542

X3X4

0.15

1

0.15

0.085

0.7753

X12

99.81

1

99.81

57.01

<0.0001

X22

55.45

1

55.45

31.68

<0.0001

X32

180.50

1

180.50

103.11

<0.0001

X42

13.62

1

13.62

7.78

0.0145

Residual error

24.51

14

1.75

Lack of fit

21.65

10

2.16

3.03

0.1486

Pure error

2.86

4

0.72

Ttotal dispersion

600.27

28

correlation coefficient (R2)

0.9592

Adjusted determination coefficient (Radj2)

0.9183