This type of longitudinal research studies the same individuals over an extended period of time.

A panel study is the longitudinal design that follows the very same individuals over an extended period.

Repeated measurement of one cohort reveals change within each person over time.

A trend study samples different people from the same population at each time point.

A cross-sectional study observes many groups only once at a single point in time.

A snapshot study is not a recognised longitudinal design and captures only one moment.

Panel studies risk attrition as participants drop out across successive waves.