Mixed Methods Longitudinal Research

Longitudinal research holds great promise for researching change and continuity. Qualitative and quantitative longitudinal research can be combined within a mixed methods framework, which enables gaining complementary insights that are more nuanced and more valid. However, longitudinal research generally entails more practical challenges than cross-sectional research. Further, combining qualitative and quantitative strategies in mixed methods longitudinal research (MMLR) multiplies these challenges. In this publication, I start by conceptualizing qualitative and quantitative longitudinal research and highlighting their respective strengths and challenges. I subsequently outline design options and implications of mixed methods longitudinal projects. Hereby, I distinguish traditional dimensions of mixed methods and longitudinal research designs, such as time and timing, priority, purpose, sampling, data collection, analysis and interpretation, and reporting. In MMLR these dimensions have an extended time dimension because these design decisions have to be made or revisited in each wave. With this contribution, I aim to advance conceptual thinking in an area of research that is certainly underdeveloped, but has great potential.