Time of participation effect and grade-orientation

The motivation and academic performance of research participants depends on the time of the semester in which the research is conducted. Therefore, data collected only once during an academic term may not adequately sample the participant pool. Sixty-eight undergraduates enrolled in various sections of an introductory psychology course participated in this research. Approximately every 2 weeks for 13 weeks, a different group of 5–16 participants completed two motivation orientation questionnaires. Participation was voluntary and participants received extra credit for participating. Participants during the last 6 weeks of data collection were more grade-oriented and had lower academic performance than participants during the first 6 weeks. Participants in the thirteenth week of the semester were more grade-oriented than those in the fifth or eleventh weeks. This time of participation effect poses a threat to the external and internal validity of research. Recommended approaches to reducing this threat include collecting data throughout an academic term and randomly assigning participants to the research dates.