AN ARGUMENT-BASED APPROACH TO VALIDITY

This article outlines a general, argument-based approach to validation, develops an interpretive argument for a placement test as an example, and examines some key properties of interpretive arguments. Validity is associated with the interpretation assigned to test scores rather than with the test scores or the test. The interpretation involves an argument leading from the scores to score-based statements or decisions, and the validity of the interpretation depends on the plausibility of this interpretive argument. The interpretive arguments associated with most test-score interpretations involve multiple inferences and assumptions. An explicit recognition of the inferences and assumptions in the interpretive argument makes it possible to identify the kinds of evidence needed to evaluate the argument. Evidence for the inferences and assumptions in the argument supports the interpretation, and evidence against any part of the argument casts doubt on the interpretation.