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The History of 'Correlation Does Not Imply Causation'
Dr Herbert West writes "The phrase 'correlation does not imply causation' goes back to 1880 (according to Google Books). However, use of the phrase took off in the 1990s and 2000s, and is becoming a quick way to short-circuit certain kinds of arguments. In the late 19th century, British statistician Karl Pearson introduced a powerful idea in math: that a relationship between two variables could be characterized according to its strength and expressed in numbers. An exciting concept, but it raised a new issue: how to interpret the data in a way that is helpful, rather than misleading. When we mistake correlation for causation, we find a cause that isn't there, which is a problem. However, as science grows more powerful and government more technocratic, the stakes of correlation — of counterfeit relationships and bogus findings — grow larger."
http://xkcd.com/552/
Correlation doesn't PROVE causation.... ...but it bloody well DOES suggest it, at least in the course of our daily lives.
The reason this phrase is so catchy is that it's counter-intuitive, and easily proven to be true. People love to use it as a "gotcha" phrase, PRECISELY because in regular life correlation does in fact usually imply causation.
In fact, correlation is used by most scientists to begin the hypothesis process. A power plant is built on a river, and the river starts drying up - most people would begin their analysis by checking on the power plant, and not the population of honeybees.
Your kid is alone in the kitchen. The cookie jar is (now) empty. Does his presence CONCLUSIVELY PROVE that he ate the cookies? Of course not, and a wise parent would find other evidence to draw a conclusion. But the correlation of their places in time and space, as well as a known predilection for cookies means that correlation strongly suggests an avenue of investigation (you're probably not going to start figuring out what happened by pursuing some other entirely different course).
It's the sort of empty-headed 'gotcha' phrase that's so popular and so often used without real thought behind it.
-Styopa
The people who mindlessly deny the possibility of causation are worse than those who compare everything to Hitler.
My Sig: SEGV
How about Correlation is insufficient to PROVE causation
I had the phrase "Desired: A woman who understands that correlation does not imply causality..." in my dating profile.
I married the woman who replied. Yes, I am surprised that worked as well.
Kind thoughts do not change the world
Correlation may not lead to causation... However it tends to give a clue on the causation.
For example a Correlation between the number of tattoos vs. the number of Motorcycle accidents.
Well ink in your skin doesn't cause you to get in an accident. However people who are more apt to taking risks will more likely get a tattoo. People who take more risks get into accidents more.
In terms of policy, you want to reduce motorcycle accidents, telling people you need to stop getting tattoos will not be effective. However with this correlation you may get results by posting motorcycle safety information at the tattoo parlors.
But using Correlation != causation as a way to short circuit an argument isn't that effective. Because if your goal is to dig for the truth or a solution, the correlation is important, and if the correlation seems reasonable to create the causation it is worth further investigation.
If something is so important that you feel the need to post it on the internet... It probably isn't that important.