Interpretation of dispersion effects in a robust design context

Abstract

The purpose of this paper is to discuss the interpretation of dispersion effects in un-replicated fractional factorials from a robust design perspective. We propose an interpretation of dispersion effects as manifested interactions between control factors and unobserved and uncontrolled factors, an interpretation shown to be useful in achieving robust designs. Further, we show the consequences this interpretation has on the identification of dispersion effects.

Keywords:

• Dispersion effects
• robust design
• split-plot experiments
• control factors
• noise factors
• random noise factors

Acknowledgements

We thank Dr Anders Hynén, Dr John Tyssedal, Dr Freek Huele and an anonymous referee for their helpful comments to an earlier draft of this paper. We would also like to acknowledge the financial support of the European Commission through IMS-EURobust (G1RD-CT-2002-00833), an IMS project within the Growth program, the Swedish Research Council and AB SKF – the Swedish bearing company.