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Table 2 Central composite experimental design matrix of the three investigated variables, with the total measured H 2 production for each of the experimental runs

From: Revealing the factors influencing a fermentative biohydrogen production process using industrial wastewater as fermentation substrate

Run number Variable Response
X1 X 2 X3 Total hydrogen production mean (mL)
1 -1 -1 -1 8.66
2 -1 -1 1 9.62
3 -1 1 -1 22.34
4 -1 1 1 25.23
5 1 -1 -1 8.28
6 1 -1 1 8.35
7 1 1 -1 14.67
8 1 1 1 11.92
9 -1.28 0 0 17.67
10 1.28 0 0 10.43
11 0 -1.28 0 2.97
12 0 1.28 0 27.18
13 0 0 -1.28 14.95
14 0 0 1.28 25.92
15 0 0 0 21.08
16 0 0 0 21.66