One of thing to watch out for when using RFs is when your test set doesn't have identical factor levels as your training data. Often can actually lead to a sign

One of thing to watch out for when using RFs is when your test set doesn't have identical factor levels as your training data. Often can actually lead to a significant bias in the prediction. Can't find a great paper on this but some discussion here:http://stats.stackexchange.com/questions/29446/random-forest-and-new-factor-levels-in-test-set http://stats.stackexchange.com/questions/29446/random-forest...