JOURNAL OF THE ACADEMY OF MARKETING SCIENCE SUMMER 1999Lynch / THEORY AND EXTERNAL VALIDITY Theory and External Validity

concerns require more attention in theoretical research. The author argues that one cannot “enhance ” external va-lidity by choosing one method over another. External va-lidity can only be “assessed ” by better understanding how the focal variables in one’s theory interact with moderator variables that are seen as irrelevant early in a research stream. Findings from single real-world settings and spe-cific sets of “real ” people are no more likely to generalize than are findings from single laboratory settings with stu-dent subjects. Both the laboratory and real world vary in background facets of subject characteristics, setting, con-text, relevant “history, ” and time. It is only when these fac-ets vary and we see how they interact that understanding of external validity is enhanced. For this to happen, the ob-servable “background ” factors have to be conceptualize