Which of the following is not a longitudinal design?

A cross-sectional design collects data at a single point in time, so it is not longitudinal.

A panel design follows the same individuals across repeated time points, so it is longitudinal.

A trend design studies the same population, with fresh samples, over time, so it is longitudinal.

A cohort design tracks a group sharing an event across time, so it too is longitudinal.

Longitudinal designs repeat measurement to reveal change and development over time.

The cross-sectional snapshot instead compares different groups at one moment.