Graphical approach to model adequacy based on exact and near replicates

In this paper, we present an intuitive graphical approach to model validity, which, although to some extent subjective, can be extremely valuable for both presentation and interpretation purposes. In particular, the idea behind such a procedure arises naturally through the generation of a sequence of elements derived from the residuals about a fitted graduating function, based on datum points that are identical or that are relatively close together in a multi-dimensional factor space.