S. Dı́az Dept. of Statistics and O.R., Faculty of Science University of Oviedo, Calvo Sotelo s/n, 33071 Oviedo, Spain diazsusana@uniovi.es B. De Baets Dept. of Applied Mathematics, Biometrics and Process Control Ghent University, Coupure links 653, B-9000 Gent, Belgium Bernard.DeBaets@Ugent.be S. Montes Dept. of Statistics and O.R. Nautical School, University of Oviedo, Viesques Campus, 33271 Gi...