Table 5.
Analysis of variance showing effects of treatment variables as linear or quadratic terms and interaction effects on response variables of average particle size.

Source	Degree of freedom	Fine fraction		Coarse fraction
		F value	Prov>F	F value	Prov>F
		Model	9	27.83	<0.0001	26.20	<0.0001
Liner	3	64.42	<0.0001	70.86	<0.0001
Quadratic	3	18.73	<0.0001	4.94	0.0121
Cross	3	0.33	0.8025	2.80	0.0716
R2		0.9364		0.9327
X11)	4	0.26	0.9015	55.61	<0.0001
X22)	4	3.81	0.0217	4.98	0.0077
X33)	4	58.79	<0.0001	0.45	0.7686

X₁: Mill grinding speed (rpm)
X₂: Separate reverse wheel speed (rpm)
X₃: Air classification reverse wheel speed (rpm)