A random sample of schools across Luzon is surveyed to assess the prevalence of asthma among elementary students aged 7-9 years old. What study design is illustrated?

A random sample of schools across Luzon is surveyed to assess the prevalence of asthma among elementary students aged 7-9 years old. What study design is illustrated?

• A. Cohort
• B. Cross sectional
• C. Systematic review
• D. Case control

Answer: (B)

A cross-sectional study is being illustrated. It collects data at a single point in time to determine how common asthma is among a defined population—in this case, elementary students aged 7–9 across randomly selected schools in Luzon. This snapshot yields prevalence, not incidence, and it doesn’t follow individuals over time, so it can’t establish temporality or causation. By contrast, a cohort study follows people over time to observe who develops asthma, a case-control study starts with people who have asthma and looks back at exposures, and a systematic review synthesizes results from multiple studies.

A cross-sectional study is being illustrated. It collects data at a single point in time to determine how common asthma is among a defined population—in this case, elementary students aged 7–9 across randomly selected schools in Luzon. This snapshot yields prevalence, not incidence, and it doesn’t follow individuals over time, so it can’t establish temporality or causation. By contrast, a cohort study follows people over time to observe who develops asthma, a case-control study starts with people who have asthma and looks back at exposures, and a systematic review synthesizes results from multiple studies.