To examine the stability of certain personality traits throughout the lifespan, a researcher designs a study in which 19-year-olds of three different cohorts, each a decade apart are interviewed every ten years for 40 years. this is an example of a(n) _ design.

I believe the answer is: Sequential Design

Sequential design is the combination of both longitudinal and cross-sectional design. This type of research is being done by researching several subjects from different groups, and the data is collected through a long period observation.