Express — An Expert System Utilizing Standard Statistical Packages

EXPRESS is an expert system based on the idea that complex chains of statistical analyses can be simplified using a standard package for each set of intermediate computations. This principle is illustrated by two-sample testing for equal location parameters, relying on various BMDP programs. Distributional assumptions are decided on after preliminary runs of BMDP. The system each time generates control language for the package, and then extracts relevant information from the print files produced. It is argued that such a stepwise procedure, considering basic results before proceeding to more complex analyses, is close to the actual behaviour of most statisticians. However, this approach raises fundamental questions concerning overall statistical characteristics of the strategy built into the system. It is suggested that these characteristics may be assessed through simulation.