The paper tries to answer the following question: “How should we treat ordinal data in hierarchical clustering?” The question is strongly connected to the use of questionnaires with ordinal scales in the social sciences. The results could help to differentiate among answers to the questions from questionnaires that could be considered as scale variables, those it would be better to convert to r...

The FechDeck is an ordinary deck of playing cards modified to support exploration of psychophysical methods. Card backs are printed with noise textures that span a range of densities. Faces are augmented with line segments arranged in "L" patterns. Jokers are printed with ruled faces and with backs that serve as noise standards. The FechDeck allows users to conduct threshold experiments using F...

In this paper we propose a generalization to symbolic interval valued variables of the Principal Curves and Surfaces method proposed by T. Hastie in [4]. Given a data set X with n observations and m continuos variables the main idea of Principal Curves and Surfaces method is to generalize the principal component line, providing a smooth one-dimensional curved approximation to a set of data poin...