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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/
In what sense, exactly does science grow more powerful? In my experience, sciences grows more expensive, less funded, more hyped, less understood, and overall less heeded.
Hey mate, spare a sig?
... and is becoming a quick way to short-circuit certain kinds of arguments.
... Correlation does not imply causation.
It must have been something you assimilated. . . .
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
It caused it.
rewriting history since 2109
Who says the correlations are false? Relationships besides A->B do exist.
How about Correlation is insufficient to PROVE causation
and is becoming a quick way to short-circuit certain kinds of arguments
The real problem here comes from people using that as a "short cut" to an actual argument.
On the one hand, we've done a great job at getting them to grasp that correlation does not imply causation. Now, we need to get people to understand what does - Necessary and Sufficient.
Next time someone uses that as a catch-phrase to shoot down a correlation as meaningless, ask them:
Does B require A? Necessary.
Does A lead to B? Sufficient.
QED, A causes B (or vice-versa).
Of course, my choice of the word "meaningless" there carries its own problems - Using correlation vs causation as a rhetorical shortcut to actual logic glosses over the fact that (statistically significant) correlations can have meaning (just that they don't "mean" causation). FWIW, The vast majority of modern medicine involves dealing with correlations rather than causes - "depressed people have low serotonin, prozac increases available serotonin", "people with high cholesterol have more heart attacks; lipitor reduces cholesterol". You can often use a correlation, as long as the two sides actually do link via some unknown variables. When they don't, however - Well, pirates don't prevent global warming because adding more pirates to the world doesn't somehow put us back before the industrial revolution.
Correlation suggests only Correlation. It doesn't suggest causation, but as you noted, it does suggest areas for further investigation. The relationship may or may not turn out to be directly causal.
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
The correlations are NOT "false". The relationships between the numbers are (almost always) NOT "conterfeit".
"Correlation does not imply causation" means exactly that. If the sky is dark and people are carrying around umbrellas, this does NOT imply that darkness causes umbrellas, or that umbrellas cause darkness. The causal relationship between two numbers is not determined by how often one number changes at the same time as another.
To put it another way: correlation is an *observed* behaviour, causation is a *tested* behaviour.
-- 'The' Lord and Master Bitman On High, Master Of All
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.
I go one step further, and require a basic understanding of Lorentz transformation.
And don't all of you girls here run down my mailbox, now...
The most recent popularity of "correlation does not indicate causality" is the result of the rise of anti-intellecutalism and anti-reason. It's something that stupid people say to try to sound smart, and to deny data.
Correlation is not proof, but if you see replicable continual correlation, ignoring it is dumb.
It comes from people who try to use an 18th century view that Science "creates facts", instead of "creates models that either are supported by observation or are not supported by observation". Correlation is just another observation.
It's one of the big favorites of the anti-intellectual Right and climate change deniers.
You are welcome on my lawn.
Statistics can ONLY show the degree of correlation. Statistics can never show causation. So, all you're ever going to get from statistics is correlation.
That reality escapes many.
References:
1) Although [statistical] regression cannot prove causation, no statistical method can do that,
2) Epidemiological studies can never prove causation; that is, it cannot prove that a specific risk factor actually causes the disease being studied. Epidemiological evidence can only show that this risk factor is associated (correlated) with a higher incidence of disease in the population exposed to that risk factor. The higher the correlation the more certain the association, but it cannot prove the causation.
The reality is that statistics can ONLY show you whether there is a correlation or not, and how strong it is. Then it requires other methods to suggest whether there is a causative relationship.
Causation is a pretty fuzzy philosophical topic so arguing about what it is or isn't, is not terribly useful.
...I guess. So we are telling them that Correlation and Causation have close to the same meaning, got it. Like ham isn't bacon, and yet both are strangely delicious. Mmmmmm, pig meat...sorry, go on.
....I am getting more and more confused. Goddam Irish.
.. note to lib arts folks... that superior laughing feeling is what the STEM people experience when algebra dropouts try to swim in our sea of math...
...And you win them over with your swauve, charming wit. SLAMDUNK!
It seems pretty simple to me. Correlation is 'Sometimes A and B are found together'. Causation is 'A causes B'. But go on...
Maybe the best way to explain it to a liberal arts grad would be something like the journey is different than the destination
or when you come to a fork in the road and see the road less traveled correlation is how you know its less traveled,
Wait, what?
or that its all somehow symbolic of Hemmingways Old Man And The Sea and the act of fishing is much different than the expectations about getting a fish.
Is this stats 101, or literary criticism 204?
Either that or the point of Joyce's Ulysses wasn't a numerical analysis that people walked around a hell of a lot in Ireland a hundred years ago.
STEM == Science Engineering Technology Math, I am guessing. For just a moment as I read that, I thought you were talking about some alien genetically engineered clones grown from stem cells, bent on subverting and destroying our society from with in. Too bad really, because it would have tied up the explanation nicely.
so when the smart guy says something about statistics, if the 1040EZ form baffles you and you can't find the "any" key on your keyboard, thats a good sign you should probably shut up and do what the smart guy says.
Please promise me that you will never become a school teacher
HA! I just wasted some of your bandwidth with a frivolous sig!
I would argue that correlation absolutely IMPLIES causation, but does not PROVE causation.
"Sic Semper Tyrannosaurus Rex."
It is absolutely true that correlation does not imply causation, but people seem to use it (especially on here) as if it magically refutes everything. Usually more so when they don't want it to be true, or just don't want to deal with it.
I hit you with a bat.
You are bleeding on the ground.
'But.. but.. correlation does not imply causation.. Maybe I started bleeding spontaneously...'
I will shred my adversaries. Pull their eyes out just enough to turn them towards their mewing, mutilated faces. Illyria
My statistics professor called these "lurking variables". Something might exist to cause both elements in a correlative relationship, but if it's not being considered in the analysis, the analysis of the correlation will be misleading. Yours is a great example.
Nice, but how bout correlation is a math formula, on the other hand causation has a ten page philosophical wikipedia page and even though Hume died like 300 years ago this year people are still arguing about it, with the exception that on the internet everyone agrees correlation isn't it, which I guess is at least some progress.
The reason causation has a ten page philosophical page is that on the macro scale everything is a result of and happen in conjunction with a gazillion butterfly effects that were either present or absent, in fact the physical article is quite short. Imagine for a murder every detail that happened in both the murderer's and victim's life who lead them there, they're all causally necessary but we put the blame on the killer. Not the policeman who forgot his bulletproof west at home or the kids who teased the murderer in third grade or the parents for conceiving him. It tries to give weight and quality to those causes that depends on the state of mind, say attempted arson is a lot more "dominating" relative to poor fire safety than an accident even if the fire is physically identical. And it all depends on how well the person could predict or control the chain of effects set in motion.
Causality is easy. Causal responsibility - which by the way is not just about assigning blame, but also things like credit - is very hard. For example, you are hanging off a cliff and another person clings to you but you can't hold on. Either you kick him off so he falls to his death or you both fall to your deaths. In no case is there a question of physical cause and effect, but would you philosophically cause his death by kicking him off or was he dead either way? What if you can hold on another minute, is that murder? Five minutes? Fifty years? I mean he's human, he's eventually going to die - you're not really changing the outcome. What if you're 100% sure you can pull yourself up, but only 99,9% sure you'll both fall to your deaths and a 0,1% chance that you through superhuman strength will pull you both up? It's hard not to get philosophical.
Live today, because you never know what tomorrow brings
Sea pirates are clearly a much stronger source of global cooling than Napster 'pirates'. It could be the parrots, the peg-legs, the cutlasses, or perhaps it's the value plundered by the pirates.
We better bump the number of p2p pirates up a couple orders of magnitude just to be sure.
OH, and be sure to drink rum when you copy that floppy.
We can still burn witches for being left-handed, right?
I'm trying to teach myself to set people on fire with my mind... Is it hot in here?
This reply usually confuses them enough to go away.
The problem with this is what "tested" means. There many infinite variables that have to be fixed and a finite set varied on each test (making the testing time infinite).
Most researchers assume something does not affect something and ignore it as a variable. There are many results that have false causation because an ignored variable was hiding there.