Interior analysis is the term now and again applied to analysis carried out on the fitted model in regression problem. The basic target of such analyses is the identification of the problem regions with respect to original least squares fit of the fitted model. Of particular interest is the disposition of the individual data points and their relative influence on the global measures used as the guides in subsequent stages of estimates of parameters in the successive models. Outliers from the fitted or predicted response, multivariate outliers among explanatory variables, and the points in the space of explanatory variables with great leverage on the fitted model must be recognized, and their influence evaluated before further analysis is under- taken.