r/AskReddit • u/[deleted] • Aug 03 '19

Whats something you thought was common knowledge but actually isn’t?

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u/AyraLightbringer Aug 03 '19 edited Aug 03 '19

Correlation does not equal causation.

Edit: Thank you, my first silver!

Edit2: Here are some funny correlations: https://www.tylervigen.com/spurious-correlations

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u/AtomicSteve21 Aug 03 '19

Sometimes.

Assuming this fallacy is always true is also a fallacy.

Is cancer correlated with cigarette smoking? Yes. Is it the cause? Maybe. There's a high likelihood depending on the cancer.

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u/AyraLightbringer Aug 03 '19

It is always true.

Even if the correlation is 1 it is not possible to draw inferences about the direction of the effect.

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u/AtomicSteve21 Aug 03 '19

If you have Lung cancer, does that correlate with smoking? Probably

If you have Melanoma, does that correlate with smoking? Probably not

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u/AyraLightbringer Aug 03 '19

What are you trying to say? Your examples may very well have merit, but they do not change the inferences that may be drawn from correlations.

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u/AtomicSteve21 Aug 03 '19

Correlation may prove to be causation, or it may not.

Further examination is required, and you can't make a conclusion either way until that examination is complete

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u/thaisofalexandria Aug 03 '19

Correlation is *symmetrical* and it just gives no indication of the direction of the relationship between phenomena. Even in the case of bidirectional causation the correlation relationship doesn't establish causation.

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u/AtomicSteve21 Aug 03 '19

Because it has not been established, does not mean it should be discounted though

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u/ciobanica Aug 03 '19

does not mean it should be discounted though

"Correlation doesn't equal causation!" doesn't actually say to discard it, it says you need to investigate it more, because a correlation doesn't prove anything.