9.9 KiB
If correlation is established, how relevant really is causation?
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Author: u/creekwise *
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URL: https://www.reddit.com/r/rational/comments/6lu7j9/if_correlation_is_established_how_relevant_really/
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Score: 0
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Created: 2017-07-07T15:01:17
Post:
[removed]
Comments:
u/Anderkent [+4] (9 minutes later)
Simply put, it is easier and cheaper to establish correlation than prove causation. Having established it, correlation could be said to be useful as a heuristic in different areas of decision making to refine the outcome. Let's say that you're in the medical field and notice that a certain disease is strongly correlated with certain habits, such as eating a certain food or smoking. Because the budget is tight or thorough research simply has not yet been done, you cannot prove causation. Do you tailor your treatment or preventative policy simply on the overwhelming correlation even though you can't prove causation and rather likely improve the outcome, or do you strictly follow the idealistic guidelines to not act without established causation.
Well, it depends on what the cost of trying is? By recommending that people change their habits, you are effectively trying to prove causation - if this then causes the disease to become less common, you've done it. If not, you know that the correlation is spurious.
If the change in habits is small (i.e. the cost is small), this is a reasonable thing to do.
Is it foolish or suicidal to deny factoring only correlation in personal decision making or even public policy by imposing a moral duty to satisfy a far more onerous rigor of causation.
I don't think the moral duty comes in at this stage. You have a moral duty to not tell others that the causation exists, etc; and to avoid confusing correlation with causation yourself. But that doesn't mean you can't act based on the correlation - just that you have to be aware your action may turn out to be useless.
In choosing your walking route from point A to point B at night, you can take a well lit boulevard or cut a shortcut through an alley where a group of young men are hanging out. Does avoiding the alley based on knowing that prisons are filled with young men imply a cognitive bias if you don't have research at hand that "being a young man causes violence".
Well, I would argue that you should take the boulevard because it's well lit, whereas the alley is dark. Not because young men hang out in the alley. If there was a well lit boulevard and a dark alley, and you knew young men liked to hang out on the well lit boulevard, would you argue to take the dark shortcut?
That to me seems exactly like what you want to avoid by distinguishing correlation and causation.
u/creekwise [+0] (29 minutes later)
By recommending that people change their habits, you are effectively trying to prove causation - if this then causes the disease to become less common, you've done it
It's a catch 22 because your advice to change the habit, under the prevailing cultural imperatives, will be discounted because you have not yet proven causation
Well, I would argue that you should take the boulevard because it's well lit
How about if the choice is between two seemingly similar alleys, except that one is being occupied by a group of 20 year old young men and the other by a group of old ladies? Statistically, young men are more likely to assault you.
u/Anderkent [+3] (38 minutes later)
It's a catch 22 because your advice to change the habit, under the prevailing cultural imperatives, will be discounted because you have not yet proven causation
No, it wouldn't. You shouldn't tell people that changing the habit will help. You're very much welcome to try and see whether changing the habit helps. The difference is in confidence.
How about if the choice is between two seemingly similar alleys, except that one is being occupied by a group of 20 year old young men and the other by a group of old ladies? Statistically, young men are more likely to assault you.
Since the scenario assumes no opportunity cost, then sure, go to the old ladies. I don't think anyone would oppose that.
I don't think correlation/causation ever has much impact on individual, reactive decisions - i.e. I want to get home and minimise risk of a fight. However, once you are trying to either address causes of something, or trying to generalise rules, that's when you have to watch out for acting on spurious correlations.
u/creekwise [+2] (2 hours later)
Since the scenario assumes no opportunity cost, then sure, go to the old ladies. I don't think anyone would oppose that.
I'm fairly sure you would encounter opposition if you applied the same statistical guideline (based on outward characteristics vs behavioral tendencies) in some more controversial manifestations of the same dilemma.
u/Anderkent [+2] (3 hours later)
Because usually 1. there is opportunity cost and 2. the thing being opposed is formed as a suggestion/statement (i.e. 'it is correct to avoid young men') rather than possibility (i.e. 'it may not be wrong to avoid young men')
u/LiteralHeadCannon [+3] (an hour later)
You distinguish between correlation and causation to avoid falling afoul of Goodhart's law. If X and Y tend to come together, and you want Y, so you do things that increase X, that works out fine if X causes Y, but not if the causal relationship between them is more complicated - in fact, a correlation between X and Y may exist even if deliberately going out of your way to prioritize X actually decreases Y.
u/creekwise [+0] (2 hours later)
I'm struggling to make sense out of your abstraction. Do you have a concrete example?
u/DCarrier [+3] (3 hours later)
You notice that houses with firefighters near them are more likely to be on fire. You ban firefighters. It turns out that they weren't actually causing the fire, and by getting rid of them you only made things worse.
u/creekwise [+1] (4 hours later)
that's a really good example
u/gvsmirnov [+2] (an hour later)
This should give you a good idea: http://www.tylervigen.com/spurious-correlations
u/creekwise [+0] (3 hours later)
I find these exhibits misleading and intellectually dishonest because they compare measure of no contextual intersection (I just made that term up but I think it offers some semantic value). A contextual intersection would be a medium in which causes and effects can interact. Such a medium in the example of habit vs disease would be the human organism and its general responsiveness to various intakes (such as eat too much, get fat etc) could be taken axiomatically. There appears to be little or no interactivity medium between drowning in a pool and Nicholas Cage.
u/Anderkent [+2] (3 hours later)
OK, so in biology, suppose presence of a certain gene X causes disease Y, and also causes much higher requirement for sugar in the diet. People with gene X are even more prone to Y if they're not ingesting enough sugar, because their organisms become weaker.
You will see correlation between ingestion of sugar and Y. This might lead you to suggest that the patient eat less sugar. However this will only make them more likely to catch Y, because they're now starving themselves.
Also, it sounds like isolating and confirming the 'contextual intersection' is basically equivalent to isolating and confirming causation.
u/creekwise [+1] (3 hours later)
the 'contextual intersection' is not something to be confirmed -- it is a medium within which the measures can interact
u/Anderkent [+1] (4 hours later)
Well, in that case you can make up contextual interactions for all the spurious correlations? US spending on science, space and technology vs suicides - the increased spending on science causes people to know how the world functions to a greater degree, which causes many to realise that their lives are pointless and they can't achieve anything, which leads to suicide. Contextual intersection achieved.
u/creekwise [+1] (4 hours later)
Normatively, you can designate a threshold of the number of degrees you'd have to jump through to link your measures to define the intersection. The more, the shakier your medium. The fewer, the more solid (indirect) the medium. IOW, the more jumps you make, the slipperier the slope. I hope it makes sense
u/NicolasBotCage [+1] (3 hours later)
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u/StudentOfJaynes [+2] (3 hours later)
'Causality' or 'Probabilistic Reasoning in Intelligent Systems' by Judea Pearl shows how to determine whether or not there is causality if there is correlation. Just thought I'd add this in case anyone hasn't heard of them yet.
u/None [+1] (4 hours later)
Thanks to whoever reported this. It's definitely not ratfic discussion, and frankly, I'm kinda wondering if /u/creekwise is ok.
You need to talk, dude?
u/creekwise [+0] (4 hours later)
what seems to be the problem and what does 'ratfic' mean?
u/None [+3] (7 hours later)
Read the sidebar.
u/creekwise [+1] (8 hours later)
OK -- so i see it is supposed to be fiction, which makes my post (first post ever BTW) off-topic. Is that correct ?
I was under the impression it was a non-fiction community about rational self-improvement etc. if all of this is correct, should I delete my post ?
u/None [+1] (8 hours later)
Don't worry! I deleted your post for you.