THE VALIDITY OF HEALTH ASSESSMENTS - RESOLVING SOME RECENT DIFFERENCES

The purpose of this paper is to examine what is meant by a valid measu re of health. Guyatt, Kirshner and Jaeschke propose that health tests should be designed so as to have one of several kinds of validity: ''l ongitudinal construct validity'' for those which are used for longitud inal research designs, and ''cross-sectional construct validity'' for those which are used for cross-sectional designs. Williams and Naylor argue that this approach to test classification and validation confuse s what a test purports to measure with the purpose for which it is use d, and that some tests have multiple uses. A review of the meanings of validity in the psychological test literature shows that both sets of authors use the term validity in an idiosyncratic way. Although the u se of a test (evaluated by content validity) should not be conflated w ith whether the test actually measures a specified construct (evaluate d by construct validity), if health is actually made up of several con structs (as suggested in Hyland's interactional model) then there may be an association between types of construct and types of purpose. Evi dence is reviewed that people make several, independent judgements abo ut their health: cognitive perceptions of health problems are likely t o be more sensitive to change in a longitudinal research design, where as emotional evaluations of health provide less bias in cross-sectiona l designs. Thus, a classification of health measures in terms of the p urpose of the test may parallel a classification in terms of what test s purport to measure.