Robust ANalysis Of VAriance: An approach based on the Forward Search

A simple robust method for the detection of atypical observations and the analysis of their effect in the ANOVA framework is presented. It is proposed to use a forward search procedure that orders the observations by their closeness to the hypothesized model. The procedure can be applied following two different strategies: one that adds units maintaining the relative group dimension and the other that adds only one new unit at each step of the search. The assessment of the goodness of the method is carried out through a simulation study. The method is then applied to real data. Results are presented through easy to interpret plots which are powerful in revealing the structure of the data.