A set of signs used as a scale against which a performance or product is placed in an evaluation. An example from Grant Wiggins' Glossary of Useful Terms Related to Authentic and Performance Assessments is taken from "the CAP writing test where a 5 out of a possible 6 is described: 'The student describes the problem adequately and argues convincingly for at least one solution . . . without the continual reader awareness of the writer of a 6.'"Descriptors allow assessment to include clear guidelines for what is and is not valued in student work. Wiggins adds that "[t]he word 'descriptor' reminds us that justifiable value judgments are made by know how to empirically describe the traits of work we do and do not value." (Emphasis his.)