Independent variables
Symbol
Levels
Un coded
Coded
-1
0
1
Solid: liquid ratio (w/v)
X
1
x
1
20
30
40
Microwave Power (W)
X
2
x
2
400
600
800
Temperature (°C)
X
3
x
3
70
80
90
Time (min)
X
4
x
4
30
40
50
Table 1:
Independent variable values of the process and their corresponding levels.
