Abstract

CRUZ-SALGADO, Javier. Selecting the Slack Variable in Mixture Experiment. Ing. invest. y tecnol. [online]. 2015, vol.16, n.4, pp.613-623. ISSN 2594-0732.

A mixture experiment is one where the response depends only on the relative proportions of the ingredients present in the mixture. There are different regression models used to analyze mixture experiments, such as Scheffé model, slack-variable model, and Kronecker model. Interestingly, slack-variable model is the most popular one among practitioners, especially formulators. In this paper, I want to emphasize the appealing properties of slack-variable model. I discuss: how to choose the component to be slack variable, numerical stability for slack-variable model and what transformation could be used to reduce the collinearity. Practical examples are illustrated to support the conclusions.

Keywords : condition number; mixture experiments; slack-variable model; scheffé model; variable transformation; Variance Inflation Factor (VIF).

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