Practice Observational vs Experimental Studies in Statistics

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

Observational studies observe subjects without manipulation; experiments deliberately assign treatments to establish causation.

Observational: Compare smokers to non-smokers (you didn't assign smoking). Experimental: Randomly assign people to take a drug or placebo (you controlled the treatment). Only experiments prove causation.

Example 1

easy
Classify each study as observational or experimental: (a) Researchers track the diets of 1000 people and record their cholesterol levels. (b) Researchers randomly assign 100 people to either a low-fat or high-fat diet and measure cholesterol after 6 months.

Example 2

medium
A 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.

Example 3

medium
A school wants to know if a new teaching method improves maths scores. Method 1: compare scores of students who chose the new method with those who chose the old method. Method 2: randomly assign students to each method. Which approach is better and why?

Example 4

hard
Explain why some research questions can only be studied observationally, not experimentally. Give two examples and discuss the ethical or practical reasons.
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