Ask and Ask Again: Longitudinal Research in Jewish Education

Education is by nature a process of change and growth. “Learning” implies movement from one status to another, from “before knowing” to “now knowing.” Longitudinal research, which involves the study of the same participants at multiple points in time, thus seems very well suited to the goals of research in education and allied fields. While longitudinal studies can be purely descriptive, there is often the assumption that observed change (or stasis) can be attributed to some factor internal or external to the participants. Though it is simple enough to grasp the basic idea of longitudinal research (which we might summarize as “ask and ask again”), there are complexities in sketching the contours of the approach. For example, how many data points are needed for a longitudinal study? While “two” would be an obvious answer that is accepted in the field, there are those that argue that three or more points are needed in order to ascertain growth trajectories and overcome potential measurement error (Ployhart & Vandenberg, 2010; Wang et al., 2017). What of the interval of data collection and the timespan of the study? Terman’s controversial Study of the Gifted began (as the Genetic Study of Genius) in 1921 and remaining participants were still being followed into the twenty-first century. University of Michigan’s Panel Study of Income Dynamics, which started in 1968, claims to be the “longest running longitudinal household survey in the world” (https://psidonline.isr.umich.edu/). Looking at the other side of the timespan raises some interesting issues about the nature of the approach. One might imagine a candidate for “world’s shortest longitudinal study” to go something like this: