Final answer:
Cross-sectional studies are useful for collecting demographic information and social characteristics by comparing different segments of the population at one time.
Step-by-step explanation:
For collecting demographic information, social characteristics, and behavioral patterns (SEIs), cross-sectional studies are useful. Cross-sectional studies involve comparing multiple segments of a population at a single point in time. Instead of following individuals over a period of time to observe changes, as would be done in longitudinal studies, cross-sectional studies look at different groups at the same time to find variances related to demographic or social factors. This method is efficient for collecting data at a single moment, making it possible to gather a broad overview across different groups within the population.