Many textbooks on evaluation have no subject index entry for evaluator or evaluator role, suggesting that, at least for many evaluation theorists, the definition is [Page 147]taken for granted. In general, evaluators have been assumed to be specialists who exercise their special knowledge and skills in independent, detached ways to avoid bias in their evaluative work.

Sprinkled throughout the evaluation literature is a wide array of terms used to describe the roles of evaluators in their work. The following is a list of many of those terms.

The most clearly developed aspect of evaluator roles is the distinction between internal and external evaluators. External evaluators are outside of the programs, organizations, or whatever types of evaluands they are evaluating, and their ...