What is a cross-sectional study and its limitations?

• A. A cross-sectional study tracks changes over time in the same individuals.
• B. A cross-sectional study uses random assignment.
• C. A cross-sectional study compares different groups at one point in time to infer differences; limitations include cohort effects and inability to infer development over time.
• D. A cross-sectional study collects longitudinal data.

Answer: (C)

Cross-sectional studies compare different groups at a single point in time to identify differences between them. This lets researchers quickly compare, for example, different age groups to see how outcomes differ without following anyone over years. A key limitation is cohort effects: observed differences may reflect the particular experiences of each generation rather than changes that happen as individuals grow older. Because the data are a snapshot, you can’t track how any individual's abilities or behaviors develop over time, so you can’t draw conclusions about development or causality. This contrasts with longitudinal designs, which follow the same people over time, and with approaches that use random assignment, which are experimental rather than descriptive cross-sectional studies.