A longitudinal study design assesses participants repeatedly at multiple points over weeks, months, years, or longer to identify changes and trends in a dependent variable. It can combine within-subjects and between-subjects comparisons, including treatment groups or cohorts. section 3.2.4
Use the design to:
- Detect changes that a simple before-versus-after comparison might miss. section 3.2.4
- Compare trends between mutually exclusive cohorts, randomly assigned groups, or treatment and control groups. section 3.2.4
- Select repeated-measures tests for limited time periods, or specialized methods such as survival analysis and growth curve analysis for longer follow-up. section 3.2.4
Tracking blood pressure over time
A study can measure blood pressure weekly for twelve weeks across three age cohorts, or annually for twelve years across two treatment groups and a control group. section 3.2.4
Figure 3.13 Longitudinal comparisons evaluate participants over months, years, or even lifetimes.
Use the figure to visualize repeated evaluation across months, years, or lifetimes. section 3.2.4
