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Xachariah comments on [LINK] If correlation doesn’t imply causation, then what does? - Less Wrong Discussion

4 Post author: Strilanc 12 July 2013 05:39AM

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Comment author: Xachariah 12 July 2013 05:54:47AM *  1 point [-]

Seems like a much longer (and harder to read) version of Eliezer's Causal Model post. What can I expect to get out of this one that I wouldn't find in Eliezer's version?

Correlation doesn't imply causation, but it does waggle its eyebrows suggestively and gesture furtively while mouthing 'look over there'.

-XKCD

Comment author: Qiaochu_Yuan 12 July 2013 08:16:44AM *  10 points [-]

Details? Content? Eliezer doesn't even define d-separation, for starters.

Comment author: [deleted] 12 July 2013 03:14:07PM *  0 points [-]

Do you know if there's an efficient algorithm for determining when two subsets of a DAG are d-separated given another? The naive algorithm seems to be a bit slow.

Comment author: IlyaShpitser 12 July 2013 04:22:18PM *  4 points [-]

http://www.gatsby.ucl.ac.uk/~zoubin/course05/BayesBall.pdf

Amusing name, linear time algorithm. Also amusingly I happen to have direct line of sight on the author while writing this post :).

In some sense, we know a priori that d-separation has to be linear time because it is a slightly fancy graph traversal. If you don't like Bayes Ball, you can use the moralization algorithm due to Lauritzen (described here:

http://www.stats.ox.ac.uk/~steffen/teaching/grad/graphicalmodels.pdf

see slide titled "alternative equivalent separation"), which is slightly harder to follow for an unaided human, but which has a very simple implementation (which reduces to a simple DFS traversal of an undirected graph you construct).

edit: fixed links, hopefully.

Comment author: [deleted] 13 July 2013 03:58:54AM 1 point [-]

Yeah, sadly both links are broken for me.

Comment author: Qiaochu_Yuan 13 July 2013 12:11:20AM 1 point [-]

Link is broken for me.

Comment author: RichardKennaway 12 July 2013 08:24:11AM *  3 points [-]

More detail, more mathematics, more exercises, more references. More, that's what you get. Eliezer's post is only an appetiser, and the XKCD a mere amuse-bouche.

Comment author: Manfred 12 July 2013 07:34:25AM *  3 points [-]

What can I expect to get out of this one that I wouldn't find in Eliezer's version?

Some of the useful (if you're going to use it or enjoy it, that is) math from chapters 1-3 of Pearl's book.