Table 2. Experimental design in coded factors and responses

Standard order Design point X1 X2 Y
1 1 –1 –1 27.5
2 2 –1 1 29.9667
3 3 1 –1 24.3
4 4 1 1 32.5666
5 5 –1 0 36.1
6 6 1 0 28.2667
7 7 0 –1 29.1
8 8 0 1 28.2
9 9 0 0 29.0667
10 9 0 0 29.6
11 9 0 0 29.1