Content validity: The source of my discontent.

The concept of content validity takes on special importance where invoked to justify use of a test. The term 1) refers to psychological measurement, 2) using samples of behavior, sampling both stimulus and response components, and 3) implies representativeness in sampling. Examples are given to show that content sampling may be considered a form of operationalism in defining constructs. Five conditions are proposed as necessary if one is to accept the use of a measuring instrument as a valid operational definition on the basis of content sampling alone