Correlation, Causation, and False Cause

Distinguish things that happen together from things that cause each other.

Two things are correlated when they tend to occur together or change together. Correlation alone does not prove that one causes the other. A false cause fallacy assumes causation from correlation or from sequence. One version, post hoc ergo propter hoc ('after this, therefore because of this'), assumes that because B followed A, A caused B. Worked example: 'Ice cream sales and drowning incidents both rise in the same months, so ice cream causes drowning. ' The real explanation is a third factor, hot weather, which increases both swimming and ice cream eating.

Another possibility is reverse causation, where B actually causes A. When you see a causal claim, ask three questions. Could a third factor explain both? Could the direction be reversed? Could it be coincidence? Researchers use controlled experiments, where one variable is changed while others are held steady, precisely to separate causation from correlation.

• 1Correlation means things occur together, not that one causes the other.
• 2Post hoc assumes that what came first caused what followed.
• 3Check for third factors, reverse causation, and coincidence.