thomblake comments on How to pick your categories - Less Wrong

59 [deleted] 11 November 2010 03:13PM

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Comment author: thomblake 11 November 2010 10:54:55PM 13 points [-]

When you play Twenty Questions with the universe, some questions are more useful than others.

Very quotable

Comment author: sketerpot 12 November 2010 10:45:20PM *  2 points [-]

And it brings to mind decision trees, which are essentially an automated way of playing Twenty Questions with the universe. In order to avoid over-fitting your training data, once you've constructed a complete decision tree, you go back and prune it, removing questions that are below a certain threshold of usefulness.

The usual way you do this is, you look at the expected reduction in entropy from asking a particular question. If it doesn't reduce the entropy much, don't bother asking. If you know that an animal is a bird, you don't gain much by asking "Is it an Emperor penguin?". You would reduce the entropy in your pool of possible birds more by asking if it's a songbird, or if its average adult wingspan is more than 10 cm.

SarahC's quote is not only clever, but also supported by solid math and practical application.