this paper we describe two adaptive procedures, one based on C p and the other based on crossvalidation. Still, when we have a final adaptive fit in hand, it is critical to subject it to graphical diagnostics to study its performance. The important implication of these statements is that the above choices must be tailored to each data set in practice; that is, the choices represent a modeling of the data. It is widely accepted that in global parametric regression there are a variety of choices...