Study Design Classification
This is a cohort study (Option A), as it involves dividing children into groups based on their exposure status (TV watching vs. no TV watching) and following them forward in time to observe health and developmental outcomes. 1
Key Distinguishing Features of This Study Design
The fundamental characteristic that identifies this as a cohort study is the exposure-based grouping followed by prospective observation:
- Children are divided by exposure status first (Group A: watches TV 2 hours daily; Group B: does not watch TV), then followed over time to assess outcomes—this is the hallmark of cohort methodology 1
- The temporal sequence moves from exposure → outcome, allowing assessment of causal relationships between screen time and subsequent health effects 1
Why Other Study Designs Don't Apply
Case-Control Study (Option B) - Incorrect:
- A case-control design would require starting with children who already have an outcome (e.g., obesity, behavioral problems) and then looking backward to assess their historical TV exposure 1
- This reverses the temporal sequence compared to what's described in the question
Cross-Sectional Study (Option C) - Incorrect:
- Cross-sectional studies measure exposure and outcome simultaneously at a single time point, without any follow-up period 1
- The question implies comparison over time, which cross-sectional designs cannot assess
Randomized Controlled Trial (Option D) - Incorrect:
- RCTs require random assignment of participants to exposure groups 1
- The question describes observational grouping based on existing TV viewing patterns, not experimental randomization
- Ethically, you cannot randomly assign children to watch or not watch TV for research purposes
Real-World Examples Supporting This Design
Multiple pediatric cohort studies have used this exact methodology:
- The Quebec Longitudinal Study followed children from age 2 to age 13, examining how toddler TV viewing predicted adolescent lifestyle habits—a classic prospective cohort design 2
- The 1970 British Cohort Study tracked participants for 32 years, assessing how childhood TV viewing at age 10 predicted adult viewing habits at age 42 3
- The Avon Longitudinal Study examined children with no wheeze at 3.5 years and followed them to 11.5 years to assess asthma development based on TV viewing duration 4
Common Pitfall: Students often confuse cohort studies with RCTs when groups are clearly defined. The critical distinction is whether assignment is observational (cohort) versus randomized (RCT). 1