  This paper examines the biases and performance of several uncertain inference
systems: Mycin, a variant of Mycin. and a simplified version of probability
using conditional independence assumptions. We present axiomatic arguments for
using Minimum Cross Entropy inference as the best way to do uncertain
inference. For Mycin and its variant we found special situations where its
performance was very good, but also situations where performance was worse than
random guessing, or where data was interpreted as having the opposite of its
true import We have found that all three of these systems usually gave accurate
results, and that the conditional independence assumptions gave the most robust
results. We illustrate how the Importance of biases may be quantitatively
assessed and ranked. Considerations of robustness might be a critical factor is
selecting UlS's for a given application.
