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Correlation does imply causation. It just doesn't necessarily establish it as a fact.
by logical42 13y ago
Correlation does imply causation. It just doesn't necessarily establish it as a fact.
- JoshTriplett 13y agoCorrelation correlates with causation, but "correlation correlates with causation" doesn't imply "correlation implies causation".
- logical42 13y agoDepends what you mean by 'imply'.
- foobarbazqux 13y agohttp://dictionary.reference.com/browse/imply http://dictionary.reference.com/browse/imply The third meaning is the one that "correlation does not imply causation" refers to. There is no other meaning for that word in that context.
- mortehu 13y agoAs described in the article, "correlation does not imply causation" would hold true even if you take "imply" to mean "is weak evidence for". This is due to Simpson's paradox[1], which says that correlation can be inverted when you take into account an additional distinguishing factor in your data. A specific example. Look at [2] and take the "y" axis to be "cigarettes per day" and the "x" axis to be "life expectancy in years". The overall trend is that more cigarettes leads to a shorter life. However, if we find that the blue group are people who do not inhale, and the red group are people who do inhale, the correlation is reversed for all smokers -- smoking more leads to a longer life. 1. https://en.wikipedia.org/wiki/Simpson's_paradox https://en.wikipedia.org/wiki/Simpson's_paradox 2. https://en.wikipedia.org/wiki/File:Simpson%27s_paradox_continuous.svg https://en.wikipedia.org/wiki/File:Simpson%27s_paradox_conti...
- foobarbazqux 13y agoWhere do hypotheses come from if correlation isn't weak evidence for causation?
- mortehu 13y agoUsually, you have some additional information, aside from the correlation itself. For example, instead of just knowing "some variable X correlates with some variable Y", you may know what X and Y actually are, and some facts about similar entities.
- foobarbazqux 13y agoBut don't you have that additional information in the Simpson's paradox examples?
- reeses 13y agoActually, that is precisely why you should form a hypothesis based on correlation. A properly conducted experiment should elucidate any causative link between the elements and the direction of those elements. Hypotheses are cheap. Create lots of them. Being 'wrong' about a hypothesis is awesome. It's the path of Reason. (Yes, I woke up this morning wanting to capitalize terms for definitional emphasis. Sorry.)
- logical42 13y agohttp://www.merriam-webster.com/dictionary/imply http://www.merriam-webster.com/dictionary/imply I prefer merriam-webster.
- mtviewdave 13y agoYes and no. The "imply" of "correlation does not imply causation" is a technical term from logic meaning "to be a sufficient circumstance." It does not mean "to suggest". https://en.wikipedia.org/wiki/Correlation_does_not_imply_causation https://en.wikipedia.org/wiki/Correlation_does_not_imply_cau...
- vacri 13y agoCorrelation implies relation, not causation.
- reeses 13y agoThe problem is in distinguishing Logic from biased Rhetoric. p → q is often an inappropriate conclusion based on correlation of two vectors. The common counterexample is (r → p) ∧ (r → q). Rhetorically, "correlation (does not imply|is not) causation" is often a red herring to dismiss a hypothesis that warrants further investigation, as correlation is essential for establishing causation.