After-Class Versus In-Class Data Collection: Validity Issues

Abstract

After a brief review of some of the many concerns that have already been associated with the use of college student volunteers as participants in psychological studies, another potential problem—the divergent nature of students who volunteer for after-class versus in-class data collection—is introduced in this article. More than 560 volunteers were tested either in or after class, using the Constructive Thinking Inventory (CTI; Epstein, 1993) as the primary dependent measure. A variety of significant differences were found between the group tested in class and the group tested after class, raising new validity issues about studies that would consider these groups as part of the same population. Specific differences between these groups are discussed both as a general warning to researchers and in comparison with previous findings about the nature of college student volunteers.