Setting Lower and Upper Bounds
main topic     how to 

By default, Minitab generates settings for an unconstrained design, that is, the lower bound is zero and the upper bound is one for all the components. However, in some mixture experimentation, it is necessary to set a lower bound and/or an upper bound on some or all of the components.

·    Lower bounds are necessary when any of the components must be present in the mixture. For example, lemonade must contain lemon juice.

·    Upper bounds are necessary when the mixture cannot contain more than a given proportion of an ingredient. For example, a cake mix cannot contain more than 5% baking powder.

Constrained designs (those in which you specify lower or upper bounds) produce coefficients that are highly correlated. Generally, you can reduce the correlations among the coefficients by transforming the components to pseudocomponents. For information on displaying or analyzing the design in pseudocomponents, see Specifying the units for components. For complete discussion, see [1] and [3].