Why Doesn't Correlation Imply Causation?

• French B
• Geography
• German A
• German A Lit
• German ab initio
• German B
• Global Politics
• History
• History (First Exam 2028)
• Mathematics Analysis and Approaches (AA)
• Mathematics Applications & Interpretation (AI)
• Philosophy
• Physics
• Psychology
• Psychology (First Exam 2027)
• Spanish A
• Spanish A Lit
• Spanish ab initio
• Spanish B
• Sports, exercise and health science (SEHS)
• Theory of Knowledge (TOK)
• World Religions

For example, ice cream sales and drowning incidents may have a positive correlation. It would be incorrect to conclude that buying ice cream causes drowning. A confounding variable, temperature, affects both: warm weather increases ice cream sales and the number of people swimming.

The common misconception is: "If (|r|) is close to $1$, one variable must cause the other." This is false. A value such as $r=0.95$ provides strong evidence of a linear association, but no evidence by itself about causal direction or mechanism.

Exam technique: This is AA SL 4.4 content and is commonly tested in a Paper 2 statistics or regression context because $r$ is calculated using technology. If asked to interpret a correlation, state its direction and strength, then explicitly write: "Correlation does not imply causation." If relevant, identify a plausible confounding variable and avoid causal verbs such as “causes” or “leads to.”