Table 7.

Analysis of variance (ANOVA) for angle of repose.

Source	SS	DF	MNS	F-value	P-value
Model	2639.6	9	293.29	23.44	< 0.001**
X1	196.49	1	196.49	15.70	0.0016**
X2	488.08	1	488.08	39.00	< 0.001**
X3	1613.03	1	1613.03	128.90	< 0.001**
X1 X2	0.07	1	0.07	0.005	0.9429
X1 X3	0.23	1	0.23	0.018	0.8947
X2 X3	28.77	1	28.77	22.30	0.1534
X12	309.77	1	309.77	24.75	0.0003**
X22	14.51	1	14.51	1.16	0.3011
X32	8.42	1	8.42	0.67	0.4269
Residual	162.68	13	12.51	-	-
Lack of Fit	157.79	5	31.56	51.73	< 0.001
Pure Error	4.88	8	0.61	-	-

**Indicated the significant at P < 0.01. DF referred to degree of freedom; SS referred to sum of squares; DF referred to degree of freedom; MNS referred to mean square.