Table 5.

Fit summary for FCCCD for biosorption of Pb²⁺ results.

Lack of Fit Tests
Source	Sum of Squares	df	Mean Square	F-value	P-value Prob > F
Linear	832.65	37	22.50	9.86	0.0021*
2FI	541.91	27	20.07	8.79	0.0032*
Quadratic	14.03	22	0.64	0.28	0.9899

Sequential Model Sum of Squares
Source	Sum of Squares	df	Mean Square	F-value	P-value Prob > F
Linear vs Mean	445.36	5	89.07	4.62	0.0018*
2FI vs Linear	290.74	10	29.07	1.77	0.1044
Quadratic vs 2FI	527.88	5	105.58	102.03	< 0.0001*

Model Summary Statistics
Source	Standard deviation	R-Squared	Adjusted R-Squared	Predicted R-Squared	PRESS
Linear	4.39	0.3442	0.2696	0.1588	1088.48
2FI	4.05	0.5689	0.3787	0.1495	1100.53
Quadratic	1.02	0.9768	0.9608	0.9474	68.01

“* Significant values, df : degree of freedom, PRESS: sum of squares of prediction error, two factors interaction: 2FI”.