| Run no. | Coded values | Real values | % biosorption of chromium | |||||||
| x1 | x2 | x3 | x4 | X1 | X2 | X3 | X4 | Experimental | Predicted | |
| 1 | −1 | −1 | −1 | −1 | 3 | 15 | 15 | 293 | 80.960 | 80.936 |
| 2 | −1 | −1 | −1 | 1 | 3 | 15 | 15 | 313 | 82.960 | 82.842 |
| 3 | −1 | −1 | 1 | −1 | 3 | 15 | 25 | 293 | 82.720 | 82.655 |
| 4 | −1 | −1 | 1 | 1 | 3 | 15 | 25 | 313 | 82.980 | 83.034 |
| 5 | −1 | 1 | −1 | −1 | 3 | 25 | 15 | 293 | 80.360 | 80.234 |
| 6 | −1 | 1 | −1 | 1 | 3 | 25 | 15 | 313 | 81.620 | 81.593 |
| 7 | −1 | 1 | 1 | −1 | 3 | 25 | 25 | 293 | 81.970 | 82.066 |
| 8 | −1 | 1 | 1 | 1 | 3 | 25 | 25 | 313 | 81.810 | 81.897 |
| 9 | 1 | −1 | −1 | −1 | 5 | 15 | 15 | 293 | 80.870 | 80.745 |
| 10 | 1 | −1 | −1 | 1 | 5 | 15 | 15 | 313 | 82.060 | 81.989 |
| 11 | 1 | −1 | 1 | −1 | 5 | 15 | 25 | 293 | 81.540 | 81.593 |
| 12 | 1 | −1 | 1 | 1 | 5 | 15 | 25 | 313 | 81.220 | 81.309 |
| 13 | 1 | 1 | −1 | −1 | 5 | 25 | 15 | 293 | 81.110 | 81.081 |
| 14 | 1 | 1 | −1 | 1 | 5 | 25 | 15 | 313 | 81.750 | 81.777 |
| 15 | 1 | 1 | 1 | −1 | 5 | 25 | 25 | 293 | 81.960 | 82.040 |
| 16 | 1 | 1 | 1 | 1 | 5 | 25 | 25 | 313 | 81.160 | 81.209 |
| 17 | −2 | 0 | 0 | 0 | 2 | 20 | 20 | 303 | 81.470 | 81.525 |
| 18 | 2 | 0 | 0 | 0 | 6 | 20 | 20 | 303 | 80.690 | 80.647 |
| 19 | 0 | −2 | 0 | 0 | 4 | 10 | 20 | 303 | 80.510 | 80.607 |
| 20 | 0 | 2 | 0 | 0 | 4 | 30 | 20 | 303 | 79.890 | 79.805 |
| 21 | 0 | 0 | −2 | 0 | 4 | 20 | 10 | 303 | 80.350 | 80.590 |
| 22 | 0 | 0 | 2 | 0 | 4 | 20 | 30 | 303 | 81.970 | 81.742 |
| 23 | 0 | 0 | 0 | −2 | 4 | 20 | 20 | 283 | 83.690 | 83.754 |
| 24 | 0 | 0 | 0 | 2 | 4 | 20 | 20 | 323 | 84.880 | 84.829 |
| 25 | 0 | 0 | 0 | 0 | 4 | 20 | 20 | 303 | 85.280 | 85.280 |
| 26 | 0 | 0 | 0 | 0 | 4 | 20 | 20 | 303 | 85.280 | 85.280 |
| 27 | 0 | 0 | 0 | 0 | 4 | 20 | 20 | 303 | 85.280 | 85.280 |
| 28 | 0 | 0 | 0 | 0 | 4 | 20 | 20 | 303 | 85.280 | 85.280 |
| 29 | 0 | 0 | 0 | 0 | 4 | 20 | 20 | 303 | 85.280 | 85.280 |
| 30 | 0 | 0 | 0 | 0 | 4 | 20 | 20 | 303 | 85.280 | 85.280 |