Textual Data Analysis for Open-Questions in Repeated Surveys

The paper addresses the problem of analysing answers to an open question observed in different waves of a repeated survey. Multiway data analysis techniques can offer interesting tools for doing that. Unfortunately, dealing with textual data some peculiar problems arise. The aim of this paper is to propose the use of non-symmetrical data analysis techniques in order to follow lexical behaviours with respect to a set of explanatory numerical variables, defining groups through time. Furthermore, attention is paid to the definition of a conjoint vocabulary.