Title

In Defense of External Validity: Do College Student Samples Yield Different Results?

Date of Completion

January 2011

Keywords

Psychology, Social

Degree

Ph.D.

Abstract

Using samples of college students is a common practice in social psychology, with some journals' studies including up to 98% college student samples. This practice receives criticism from both within the field and without, usually on the basis that samples of college students lack external validity. This assumption of differences between college students and other adults remains largely untested. Presented here first are two studies that investigated whether there are main effect differences between college students and other adults on personality outcome measures. These first two studies used meta-analytic and other techniques to investigate differences between college students and other adults. The third study replicated five classic studies in social psychology, with samples of college students and other adults, in order to investigate whether the results of each study were different for college students and other adults. This third study investigated the interaction effect, or whether the effect under investigation in the study interacted with the type of sample. Finally, the fourth study used a sample of social psychologists and asked them to predict the outcomes from the third study, in order to investigate whether social psychologists tend to agree that college students differ from other adults. Results from all studies show a small number of small main effect differences but never an interaction effect. These results are strong evidence against the hypothesis of large, widespread differences between college students and other adults. ^