Today I want to concentrate on the foundation of what is most commonly taught as design of experiments (DOE)—factorial designs.

Elsewhere I’ve mentioned three of C.M. Hendrix’s “ways to mess up an experiment.” After 35 years of teaching DOE, I’ve concluded that he pretty much captures the universal initial class experience I described in these additional ways to mess up:
• No comprehensive strategy, i.e., attacking one dependent variable at a time
• Too many experiments concentrated in one region of experimental space, or too few variables
• Attempting to optimize by manipulating one variable at a time
• Failure to appreciate the role of interactions

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