Table 1.

Comparison of recurrent cross-sectional and trajectory analysis

Considerations	Recurrent cross-sectional analysis	Trajectory analysis
Research focus	Describe the differences between time points	Describe how process or experience changes over time
Sample considerations	The cohort at each time point may be the same or different May be preferred if sample is highly transient or has high mortality over study duration	Must maintain same cohort
Theoretical approach	Determined by the research question Any analytic approach may be used consistently throughout the study	Determined by the research question Any analytic approach may be used consistently throughout the study
Level of data analysis	Whole sample (or subsamples)	Individual people or individual groups (e.g., families)
Timing of analysis	May analyze as each time point is completed	Must wait until data is collected at all time points