What is the difference between cross-sectional and longitudinal normative data?

• A. Cross-sectional norms are from multiple reference samples, while longitudinal norms track how scores change within individuals over time.
• B. Cross-sectional norms track changes within individuals over time, while longitudinal norms use a single reference sample.
• C. Cross-sectional norms are from a single reference sample, while longitudinal norms track how scores change within individuals over time.
• D. Cross-sectional norms are used to predict future performance, while longitudinal norms describe past performance.

Answer: (C)

Normative data come in two flavors to show how a score fits with typical development. Cross-sectional norms are built from a single reference sample collected at one point in time across different ages, giving age-based benchmarks you can compare a person’s score to right now. Longitudinal norms, by contrast, follow the same individuals across multiple time points, showing how scores change within each person as they develop. So the key difference is whether the data provide a snapshot from many people at one time (cross-sectional) or a trajectory for the same people over time (longitudinal).

The statement that cross-sectional norms come from a single reference sample and longitudinal norms track how scores change within individuals over time aligns with this distinction.