Table 2.

Analysis of variance for biosorption of Congo red by Ulva lactuca biomass obtained by FCCCD.

Source of variance		Degrees of freedom	Sum of square	Mean of square	F-value	P-value	Coefficient estimate
Model		20	22,728.56	1136.43	271.25	< 0.0001*	93.67
Linear effect	X1	1	261.77	261.77	62.48	< 0.0001*	− 2.77
	X2	1	11.38	11.38	2.72	0.1101	0.58
	X3	1	1172.94	1172.94	279.96	< 0.0001*	5.87
	X4	1	1504.90	1504.90	359.19	< 0.0001*	− 6.65
	X5	1	1466.42	1466.42	350.01	< 0.0001*	− 6.57
Interaction effect	X1X2	1	227.64	227.64	54.33	< 0.0001*	− 2.67
	X1X3	1	45.20	45.20	10.79	0.0027*	− 1.19
	X1X4	1	319.98	319.98	76.37	< 0.0001*	3.16
	X1X5	1	28.67	28.67	6.84	0.0140*	0.95
	X2X3	1	381.09	381.09	90.96	< 0.0001*	3.45
	X2X4	1	520.60	520.60	124.26	< 0.0001*	− 4.03
	X2X5	1	346.17	346.17	82.63	< 0.0001*	− 3.29
	X3X4	1	656.76	656.76	156.76	< 0.0001*	4.53
	X3X5	1	315.44	315.44	75.29	< 0.0001*	3.14
	X4X5	1	440.97	440.97	105.25	< 0.0001*	− 3.71
Quadratic effect	X12	1	16.47	16.47	3.93	0.0569	2.58
	X22	1	14.66	14.66	3.50	0.0716	− 2.43
	X32	1	32.76	32.76	7.82	0.0091*	− 3.64
	X42	1	62.06	62.06	14.81	0.0006*	− 5.01
	X52	1	2219.22	2219.22	529.69	< 0.0001*	− 29.95
Error effect	Lack of Fit	22	107.87	4.90	2.52	0.1062
	Pure Error	7	13.63	1.95
R2	0.9947	Std. Dev	2.05
Adj R2	0.9910	Mean	67.52
Pred R2	0.9843	C.V. %	3.03
Adeq Precision	63.80	PRESS	358.04

“* Significant values, F: Fishers's function, P: Level of significance, C.V: Coefficient of variation”.