This paper is a contribution to conceptions description methods. The approach considers every conception about a concept, as constituted of a limited number of features or dimensions, previously identified. A “progressive selecting questionnaire” has permitted to collect data which monitoring necessitated the elaboration of a Barycentre Model of Data Treatment (BMDT). The latter allows, for every dimension, the calculation of “a barycentre indication”, used as a criterion of dimensions classification, thus revealing the conceptions structure of a subject or a group. The model has been tested on data about problem solving conceptions, collected from a sample of 179 physics and chemistry secondary school teachers, in Senegal. The outcomes showed that the BMDT is a relevant tool for conceptions description in education field, with transfer possibilities to health, culture, economy, etc.