DOE Variables

Variables

System parameters that can be changed to improve the system performance.

Reduced Variables

In DOE terminology, it is standard practice to work with reduced variables that have a range of -1 to 1 for each real variable. Reduced variables are associated to real variables with the following formula:

y = \frac{x - \frac{(x_{\max} + x_{\min})}{2}}{\frac{x_{\max} - x_{\min}}{2}}

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.