Source

S (sum of squares)

Φ (DF)

Ψ (mean square)

χ (F value)

τ (Prob. > F)

Model

11.78

16

0.74

10.97

<0.0001

X₁-collector dose

0.66

1

0.66

9.87

0.0085

X₂-pH

0.32

1

0.32

4.84

0.0482

X₃-flotation speed

0.34

1

0.34

5.06

0.0440

X₄-air flow rate

2.77

1

2.77

41.29

<0.0001

X₁X₄

1.08

1

1.08

16.11

0.0017

X₂X₃

0.51

1

0.51

7.61

0.0173

X₂X₄

0.38

1

0.38

5.73

0.0340

X₃X₄

0.60

1

0.60

8.95

0.0113

$X_1^2$

0.081

1

0.081

1.20

0.2946

$X_2^2$

0.016

1

0.016

0.24

0.6303

$X_3^2$

0.29

1

0.29

4.30

0.0603

$X_4^2$

3.84

1

3.84

57.24

<0.0001

$X_1^2{X}_2$

0.097

1

0.097

1.44

0.2530

$X_1^2{X}_4$

0.70

1

0.70

10.46

0.0072

$X_2^2{X}_4$

2.01

1

2.01

29.94

0.0001

$X_2{X}_3^2$

0.49

1

0.49

7.23

0.0197

Residual

0.81

12

0.067

Lack of Fit

0.65

8

0.081

2.08

0.2504