Study Design Classification
This is a cohort study (Option A). The scenario describes dividing children into two groups based on their exposure status (TV watching vs. no TV watching) and would typically involve following them forward in time to observe outcomes.
Key Features That Define This as a Cohort Study
Exposure-based grouping: Participants are classified according to their exposure status—Group A (watches TV 2 hours daily) versus Group B (does not watch TV)—which is the fundamental characteristic of cohort design 1, 2.
Temporal sequence: In a cohort study, participants do not have the outcome of interest at baseline; they are selected based on exposure status and then followed over time to evaluate for occurrence of outcomes 1.
Forward direction: Cohort studies track groups forward from exposure to outcome, establishing clear temporality between exposure and disease 2.
Why Other Options Are Incorrect
Not a Case-Control Study (Option B)
- Case-control studies work in the opposite direction—they start with individuals who already have the outcome (cases) and those who don't (controls), then look backward to assess past exposures 2.
- The question describes grouping by exposure (TV watching), not by outcome status.
Not a Cross-Sectional Study (Option C)
- Cross-sectional studies assess exposure and outcome simultaneously at a single point in time 3.
- The described scenario involves grouping based on ongoing exposure behavior (daily TV watching), which implies a longitudinal follow-up component typical of cohort studies 1, 4.
Not a Randomized Controlled Trial (Option D)
- RCTs involve random assignment of participants to intervention groups 1.
- The question describes observational grouping based on existing TV-watching behavior, not randomized allocation.
Clinical Context
Cohort studies are particularly well-suited for studying the effects of TV exposure in children because they allow researchers to establish temporal relationships between screen time and developmental or health outcomes 5. The longitudinal nature permits assessment of multiple outcomes following a single exposure, making this design efficient for examining various effects of TV watching on child development 2, 4.