Observational vs Experimental Studies Statistics Example 2
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Example 2
mediumA study finds that people who drink green tea have lower rates of heart disease. The study surveyed 5000 tea drinkers and 5000 non-tea drinkers. Can we conclude that green tea prevents heart disease? Explain, identifying the type of study.
Solution
- 1 Step 1: This is an observational study — researchers did not assign people to drink or not drink green tea; they observed existing behaviour.
- 2 Step 2: Observational studies cannot establish causation because confounding variables may exist. Green tea drinkers might also exercise more, eat healthier, or have other healthy habits.
- 3 Step 3: To establish causation, a randomised controlled experiment would be needed: randomly assigning people to drink green tea or a placebo and controlling other variables.
Answer
No, we cannot conclude green tea prevents heart disease. This observational study can only show association, not causation, because confounding variables (diet, exercise, lifestyle) may explain the difference.
Observational studies are valuable for identifying associations and generating hypotheses, but they cannot prove causation due to potential confounding variables. The gold standard for causal evidence is the randomised controlled experiment.
About Observational vs Experimental Studies
Observational studies gather data by watching subjects in their natural setting without any intervention, while experimental studies deliberately assign treatments to subjects and measure the outcomes. Only experiments, through random assignment, can establish cause-and-effect relationships.
Learn more about Observational vs Experimental Studies →More Observational vs Experimental Studies Examples
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