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Correlation does not imply causation is a phrase used in the sciences and statistics to emphasize that correlation between two variables does not imply there is a cause-and-effect relationship between the two.
Its converse, correlation implies causation, is a logical fallacy by which two events that occur together are claimed to have a cause-and-effect relationship.
It is also known as cum hoc ergo propter hoc (Latin for "with this, therefore because of this") and false cause. It is subtly different to the fallacy post hoc ergo propter hoc, which in requiring a chronological component may be considered a subtype of cum hoc.
From the Wikipedia - which is much more comprehensive than the New Standard Encyclopedia I had as a kid (still have).
Can't wait to casually lob that into a conversation.