DOE Simplified, 3rd Edition

Chapter 2

Simple Comparative Experiments

Many of the most useful designs are extremely simple.

Sir Ronald Fisher

We now look at a method for making simple comparisons of two or more “treatments,” such as varying brands of toothpaste, and testing their efficacy for preventing cavities. Called the F-test, it is named after Sir Ronald Fisher, a geneticist who developed the technique for application to agricultural experiments. The F-test compares the variance among the treatment means versus the variance of individuals within the specific treatments. High values of F indicate that one (or more) of the means differs from another. This can be very valuable information when, for example, you must select from several suppliers or materials or levels ...