In a cross-sectional study, which description is accurate?

In a cross-sectional study, which description is accurate?

• A. A study that follows individuals over time to observe outcomes
• B. A study that randomly assigns treatment to evaluate efficacy
• C. A study that compares cases with controls
• D. A study in which a representative cross section of the population is tested or surveyed at one specific time

Answer: (D)

Cross-sectional studies capture a single moment in time by surveying or testing a representative sample of the population at one point. This design provides a snapshot of how things are at that moment, often used to estimate prevalence and to look for associations between variables present at that time. Because data are collected only once, you can’t determine which came first or whether one factor caused another. The description you’re looking for fits the idea of surveying a representative cross section of people at one specific time. Why the other descriptions don’t fit: following people over time to observe outcomes describes a longitudinal or cohort approach; randomly assigning treatment to evaluate efficacy describes a randomized controlled trial; and comparing people with a disease (cases) to those without (controls) describes a case-control study. Each of those designs involves time in some form, selection based on future outcomes, or deliberate manipulation, unlike a single-time cross-sectional survey.

Cross-sectional studies capture a single moment in time by surveying or testing a representative sample of the population at one point. This design provides a snapshot of how things are at that moment, often used to estimate prevalence and to look for associations between variables present at that time. Because data are collected only once, you can’t determine which came first or whether one factor caused another.

The description you’re looking for fits the idea of surveying a representative cross section of people at one specific time.

Why the other descriptions don’t fit: following people over time to observe outcomes describes a longitudinal or cohort approach; randomly assigning treatment to evaluate efficacy describes a randomized controlled trial; and comparing people with a disease (cases) to those without (controls) describes a case-control study. Each of those designs involves time in some form, selection based on future outcomes, or deliberate manipulation, unlike a single-time cross-sectional survey.