Term Effect Coef SE Coef T* P**
Constant   81.369 0.4475 181.83 0.000
Main Factors  
X -4.815 -2.408 0.4475 -5.38 0.001
pH -0.556 -0.278 0.4475 -0.62 0.552
BD 10.525 5.263 0.4475 11.76 0.000
Interaction of two factors  
X.pH 7.533 3.767 0.4475 8.42 0.000
X.BD 8.572 4.286 0.4475 9.58 0.000
pH.BD -7.143 -3.572 0.4475 -7.98 0.000
Interaction of three factors  
X.pH.BD -9.954 -4.977 0.4475 -11.12 0.000
*T= t-test, **P=Propabiliy level
Table 4: Statistical parameters for full 23 factorial design of Pb2+ biosorption.