DOE Variables
Common terminology in a DOE.
Variables
System parameters that can be changed to improve the system performance.
Reduced Variables
where x is the initial variable, and y is the reduced variable.
Levels
Values taken by y in the range [-1; +1]. The number of levels per variable to be considered depends on the level of non-linearity in the problem; for a linear model two levels are sufficient; for a quadratic model three levels are needed.