Change? What change? An exploration of the use of mixed-methods research to understand longitudinal measurement variance

A primary objective of panel studies is to analyze change. The same questionnaire is used to compare data recorded at various times. Panel designs assume that the meaning of the questions and the concept of interest are stable over time. Analyses of measurement invariance often show the contrary. A qualitative part supplementing a panel survey can help us understand this phenomenon. In this study, 261 first-year psychology students completed questionnaires about their study motivation on two occasions; we interviewed some students as well. The survey showed that study motivation is not invariant over time. The qualitative data converged with the quantitative outcomes and explained the lack of invariance by the students' overall transition during the first study year.We conclude that mixing quantitative and qualitative research methods for panel studies helps us understand change in constructs over time. We can study change at the macrolevel and better understand such change at the microlevel. © 2011 Hogrefe Publishing.