Stavex: A Sophisticated but User-Friendly Expert System for the Design and Analysis of Experiments

Abstract

STAVEX enables experimenters in research and development to apply statistical design and analysis of experiments in their routine work independently of a statistician. STAVEX presents expert knowledge in industrial statistics in the language of practitioners. The system can handle process factors, such as temperature or concentration, as well as mixture factors which have to satisfy a summing-up condition, for example, typical in galenic formulations.

The STAVEX philosophy is based on the three typical stages of statistical experimental design: screening, modeling, and optimization. During the first two stages the goal is factor reduction. It is recommended to begin experimentation with a large (say more than eight) number of factors. In the final optimization stage, the number of factors is small (three or less); then, a quadratic model is fitted which should allow for good predictions.

STAVEX guides the users through these different experimentation stages, writes reports, suggests a look at appropriate graphical displays (such as half-normal plots or overlaid contour plots) to help in the interpretation and understanding of the results, and provides extensive model diagnostics concerning outlier detection, transformations, and model deviations. STAVEX runs on PCs under Microsoft Windows 3.1, Windows NT, or Windows 95.