Mixture-Process Variable Designs
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Process variables are factors in an experiment that are not part of the mixture but may affect the blending properties of the mixture. For example, the adhesive properties of a paint may depend on the temperature at which it is applied.

You can include up to seven two-level process variables in the mixture design. The process variables may be included as full or fractional factorial designs. The mixture design will be generated at each combination of levels of the process variables or at a fraction of the level combinations.