Table 3.

Analysis of variance for adsorption of chromium by E. intestinalis obtained by the FCCCD.

Source of variance		Degrees of freedom	Sum of square	Mean of square	F-value	P-value	Coefficient estimate
Overall model		20	6,714.68	335.73	199.94	< 0.0001*	73.82
Linear effect	X1	1	3,936.38	3,936.38	2,344.29	< 0.0001*	10.76
	X2	1	115.02	115.02	68.50	< 0.0001*	1.84
	X3	1	19.60	19.60	11.67	0.0019*	− 0.76
	X4	1	145.84	145.84	86.86	< 0.0001*	2.07
	X5	1	265.00	265.00	157.82	< 0.0001*	− 2.79
Interaction effect	X1X2	1	77.90	77.90	46.39	< 0.0001*	− 1.56
	X1X3	1	553.45	553.45	329.61	< 0.0001*	4.16
	X1X4	1	4.94	4.94	2.94	0.0971	0.39
	X1X5	1	42.06	42.06	25.05	< 0.0001*	1.15
	X2X3	1	1.70	1.70	1.01	0.3222	− 0.23
	X2X4	1	102.03	102.03	60.77	< 0.0001*	1.79
	X2X5	1	61.97	61.97	36.90	< 0.0001*	− 1.39
	X3X4	1	49.62	49.62	29.55	< 0.0001*	− 1.25
	X3X5	1	121.89	121.89	72.59	< 0.0001*	1.95
	X4X5	1	0.43	0.43	0.26	0.6162	0.12
Square effect	X12	1	649.80	649.80	386.99	< 0.0001*	− 16.21
	X22	1	40.90	40.90	24.36	< 0.0001*	4.07
	X32	1	41.00	41.00	24.42	< 0.0001*	− 4.07
	X42	1	380.06	380.06	226.34	< 0.0001*	12.40
	X52	1	10.73	10.73	6.39	0.0172*	− 2.08
Error effect	Lack of fit	22	41.74	1.90	1.91	0.1927
	Pure error	7	6.95	0.99
R2	0.9928	Std. dev	1.30
Adj R2	0.9878	Mean	69.81
Pred R2	0.9754	C.V. %	1.86
Adeq precision	49.34	PRESS	166.15

*Significant values, F: Fishers's function, P level of significance, C.V coefficient of variation.