  For any system with limited statistical knowledge, the combination of
evidence and the interpretation of sampling information require the
determination of the right reference class (or of an adequate one). The present
note (1) discusses the use of reference classes in evidential reasoning, and
(2) discusses implementations of Kyburg's rules for reference classes. This
paper contributes the first frank discussion of how much of Kyburg's system is
needed to be powerful, how much can be computed effectively, and how much is
philosophical fat.
