The distinction between variables that change together (correlation) and one variable actually causing changes in another (causation). A correlation shows a relationship exists, but doesn't prove that one variable causes the other.
Correlation from Latin correlatus (mutually related) emerged in statistics in the 1840s, while causation from Latin causatio dates to medieval philosophy. The phrase became prominent in 20th-century scientific methodology as researchers emphasized the need to distinguish association from causal relationships.
Ice cream sales and drowning deaths are correlated, but ice cream doesn't cause drowning—hot weather causes both! This fundamental confusion underlies countless misconceptions in health, education, and social policy.
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