Let È´Ý Üµ be an unknown conditional distribution over inputs, Ü, and output classes, Ý ¾ Ý ½ , Ý ¾ , ¡ ¡ ¡ , Ý Ò , and let È´Üµ be the marginal 'input' distribution.
this is a difficult learning task and generalization to the test set is quite reasonable.