Table 4.

Experimental design by using CCD, experimental value and predicted value

Run	x 1	x 2	x 3	Experimental value (µg/L)	Predicted value (µg/L)	Residual
1	−1	1	1	482.32	483.16	−0.84
2	0	0	0	536.84	539.66	−2.82
3	0	0	0	534.15	539.66	−5.51
4	−1	−1	1	397.65	407.10	−9.45
5	0	0	0	545.20	539.66	5.54
6	1	−1	−1	500.43	507.12	−6.69
7	−1	1	−1	438.56	450.54	−11.98
8	0	−1.682	0	465.94	459.06	6.88
9	0	0	0	532.35	539.66	−7.31
10	0	0	0	538.06	539.66	−1.60
11	−1	−1	−1	411.17	417.12	−5.95
12	0	1.682	0	445.41	541.61	3.80
13	0	0	−1.682	486.10	476.23	9.87
14	1	−1	1	529.24	524.82	4.42
15	0	0	0	549.52	539.66	9.86
16	1.682	0	0	556.87	559.33	−2.46
17	−1.682	0	0	407.31	394.15	13.16
18	1	1	−1	531.13	529.22	1.19
19	1	1	1	587.96	589.56	−1.60
20	0	0	1.682	519.37	518.55	0.82