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. 2013 Oct 7;6:144. doi: 10.1186/1754-6834-6-144

Table 4.

Coded values of the variables for the central composite design

    Actual values of coded levels    
Variables
Coded symbol
-1
0
1
-1.6818
1.6818
-Inoculum age (h)
X1
24
48
72
8.00
88
Nitrogen content (mg)
X2
200
300
400
132
468
Substrate (g) X3 1.5 2.0 2.5 1.16 2.84