Cross-sectional vs. longitudinal designs
Researchers test memory in 30-, 50-, and 70-year-olds at the same time. A key weakness of this design is:
Answer B: explanation for every choice
A
Attrition is a weakness of longitudinal designs, which follow the same people over time.
B
Correct. In a cross-sectional design, people of different ages also grew up in different eras, so differences may reflect generation rather than age.
C
Long follow-up is a cost of longitudinal designs.
D
Practice effects arise when the same people are tested repeatedly, as in longitudinal designs.
TakeawayCross-sectional: fast but confounded by cohort. Longitudinal: tracks change but slow, with attrition.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID ps94.