Does theory work in practice? Two case studies

ABSTRACT

Case studies offer an opportunity to review what worked and what didn't and to draw conclusions about what changes to make in future projects. This article presents two different studies. Each study explored the properties of a production process and each had a number of issues to be resolved before experimental runs could be performed. In the first case, the process was a continuous rubber extrusion line, producing windscreen wiper blades. Planning involved people on three different continents, so issues of building trust were paramount. Only a narrow time window was available for experimentation, so flexibility and a quick response to problems as they arose were needed. The second study was an off-line batch process aimed at producing polymers suitable for artificial corneas. There were two competing variables of interest. Previous attempts to improve the product had been piecemeal and unsuccessful, but a fractional factorial experiment provided guidance on a way forward. Subsequent runs then aimed to optimize the primary variable whilst holding the second variable constant. By comparing and contrasting these studies, many valuable lessons can be learned.

KEYWORDS:

• case studies
• experimental design
• factorial experiments
• multiple objectives
• optimizing processes
• response surface designs

About the author

Richard Jarrett is now a Visiting Research Fellow at the University of Adelaide, having recently retired from CSIRO, a government funded research facility in Australia, where he worked as a statistician for 30 years, in areas as diverse as mineral processing, animal health, forestry and risk management. He also spent 9 years as Professor of Statistics at the University of Adelaide.