An Application of Taguchi's Methods Reconsidered

Two aspects of Taguchi's methods for analyzing parameter design experiments that can be improved upon are considered. It is shown how using interaction graphs instead of marginal graphs, and how using the sample variance instead of a signal-to-noise ratio, can lead to product designs that are more robust to variation. The advantages of the alternative analysis will be illustrated by re-analyzing a case study considered by Barker (1986)

One-Factor-at-a-Time versus Designed Experiments

Many engineers and scientists perform one-factor-at-a-time (OFAT) experiments. They will continue to do so until they understand the advantages of designed experiments over OFAT experiments, and until they learn to recognize OFAT experiments so they can avoid them. A very eective way to illustrate the advantages of designed experiments, and to show ways in which OFAT experiments present them-selves in real life, is to introduce real examples of OFAT experiments and then demonstrate why a designed experi-ment would have been better. Three engineering examples of OFAT experiments are presented, as well as designed ex-periments that would have been better. The three examples have been successfully used in an industrial workshop and can also be used in academic courses. KEY WORDS: Teaching statistics. 1