CHAPTER 14: Generalizing Results
•In this chapter, we’ll consider the issue of generalization of research findings. Recall that internal validity refers to the
ability to infer that there is a casual relationship between variables. External validity is the extent to which the findings
may be generalized.
Generalizing to other populations of research participants
•As noted in chap 7/9, individuals who participate in psychological research are usually selected because they’re
available, mostly, freshmen, college students, sophomores enrolled in the introductory psychology course.
•Are our research findings limited to these types of subjects or can we generalize our findings to a more general
•Smart found that college students were studied in over 70% of articles published between 1962-1964 in the Journal of
Experimental Psychology and the Journal of Abnormal and Social Psychology.
•Sears reported similar findings in 1980-1985 in psychology journals. The problem is that such studies use highly
restricted populations. They are young, posses characteristics of late adolescence: a sense of self-identity that is still
developing, political attitudes that are in a state of flux, need for peer approval and unstable relationships. They are
intelligent, have high cognitive skills, and know how to win approval from authority. What we know about “people in
general” may be limited to highly select and an unusual group.
•The problem of unrepresentative subjects is not confined to human research. A great deal of research relies on the white
rat: Rats are hardy, cheap, easy to rear, and well adapted to laboratory experience. Like freshmen, they are easy to
obtain on a college campus.
•Researchers usually must ask people to volunteer to participate in the research. At many colleges, it is required for the
course, or to complete an alternative project.
•If you are studying populations other than college students, you are even more dependent on volunteers. Ex: conducting
research on the internet in which people must go onto your Web page and complete the survey.
•Research indicates that volunteers tend to me more highly educated, more in need of approval and more social: they also
have higher socioeconomic status.
•Sometimes, researchers use male or females ( or a very disproportionate ratio of males to females) because this is
convenient or the procedure seems better suited to either males or females.
•Given the possible differences between males and females, the results of such studies may not be generalizable.
•Denmark et al. provide an example of studies on contraception practices that use only females because of stereotypical
assumptions that only females are responsible for contraception. They also point out other ways that gender bias may
arise in psychological research, including confounding gender with age or job status and selecting response measures
that are gender-stereotyped.
•The solution is to be aware of possible gender differences and include both male and female in research investigations.
•Participants in one locale may differ from participants in another locale. Example: students at UCLA may differ from
students in a nearby state university, who may differ from students in a community college. People in Iowa may differ
from people in New York City.
•Thus finding students in one type of educational setting in one geographic region may not generalize to people in other
settings or regions.
Generalization as a Statistical Interaction
•The problem of generalization can be thought of as an interaction in a factorial design.