ABSTRACT
Raymond B.Cattell, the author of the Sixteen Personality Factor Questionnaire (16PF), distinguished three domains (Cattell & Warburton, 1967) within which human characteristics may be assessed: the ability domain, what one can do; the motive domain, what one wants to do; and the personality domain, one's style, how one typically acts. The 16PF and other similar measures are in the personality domain. In addition to the three assessment domains, Cattell distinguished three data sources or levels (Leary, 1957) from which one may get information about a person's characteristics: life data (L-data), which consist of observations from real, everyday events, or reports of what a person does; question data (Q-data), what a person says about self—what Leary (1957) called the level of conscious communication; and test data (T-data), in which a person reacts to a set of contrived circumstances, as contrasted to the naturally occurring situations of L-data. Q-data, the form of information in which personality questionnaires are found, is the only one in which the person consciously reports about self. In the other two (L-data and T-data) the person does something that can be the basis for inference about personality.
