American journal of preventive medicine
-
To understand the external validity of experimental studies, it is important to estimate the extent to which the participants are representative of the general population. This paper describes recruitment methods and considers the representativeness of participants in the San Diego Family Health Project. The study was designed to experimentally evaluate the effectiveness of a family-based behavior change intervention in Anglo and Mexican-American families. ⋯ In separate analyses for Anglo and Mexican-American responders, our data suggested many similarities and a few differences among participant groups. The differences that were observed suggest that participants may already have healthier diets than nonparticipants, although only one of four dietary variables differed by participation status in each ethnic group. The external validity of these data and general recruitment issues are discussed.