3 This problem happens because they have no control of the words unselected by R. Intuitively, in the presence of degeneration, some key predictors in X will be left unselected by R. Thus by looking at the predictive power of R c , we can determine if degeneration occurs.
when degeneration is present, all the useful information is left unselected by R, and so H(Y |R c ) is low.