Independent variables Coded levels
Name Code -1.68 -1 0 1 1.68
Actual Levels
Temperature (°C)) X1 73.59 77 82 87 90.41
Charcoal             Thickness ( mm) X2 0.83 1 1.25 1.5 1.67
Deola   ( g/lit) X3 0.063 0.2 0.4 0.6 0.74
Table 1: Values of independent variables in coded and actual form.