“…Researchers have long been aware of the problematic nature of generalizing findings from research settings to situations and populations not specifically studied in the research. Studies conducted by psychological researchers on volunteer samples (Dura & Kiecolt-Glaser, 1990; Mandel, Weiner, Kaplan, Pelkovitz, & Labruna, 2000), undergraduate samples (Sears, 1986), and Internet-based samples (Quartaro & Spiers, 2002) have been criticized for their limited generalizability. Medical researchers have discussed the problems associated with conducting research on unrepresentative samples and the difficulty of recruiting representative samples (Sellors et al, 2002), as well as the ethical implications and limitations in generalizability associated with excluding patients from research trials (Bartlett et al, 2003; Chalmers, 1990).…”