Table 2. Design matrix for chromium stabilization experiments (coded variables)^a.

Experiment number	Coded variables
	Reagent dosage (%) (X1)	Fly ash (%) (X2)	Lime (%) (X3)
1(C)	0	0	0
2	0	1	1
3	0	−1	−1
4(C)	0	0	0
5	−1	1	0
6	1	1	0
7	−1	0	−1
8	−1	0	1
9	1	−1	0
10	1	0	1
11	0	−1	1
12(C)	0	0	0
13	0	1	−1
14	1	0	−1
15	−1	−1	0

^a C – central point of design.