Chapter 9

Mixture Design

The good things of life are not to be had singly, but come to us with a mixture.
Charles Lamb

The cliché image of experimentation is a crazed person in a lab coat pouring fluorescent liquids into bubbling beakers. Ironically, the standard approaches for design of experiments (DOE) don’t work very well on experiments that involve mixtures. The following illustration shows why.

For example, what would happen if you performed a factorial design on combinations of lemonade and apple juice? Table 9.1 shows the experimental layout with two levels of each factor—either one or two cups.

Table 9.1

Factorial design on mixture of fruit juices

Std Order

A: Lemonade (cups)

B: Apple juice (cups)

Ratio

1

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