Using data available for the survey carried out at the University of Cagliari, the main goal is defining a suitable indicator of professors’ performance built on the data collection system introduced by the Italian National Agency for the Evaluation of Universities and Research Institutes. We compare three main approaches, aimed at defining a quantitative indicator and based on algebraic manipulation of proportions arising from questionnaire items as well as orientated towards defining a qualitative indicator based on geometric and/or probabilistic arguments that are developed on the basis of the nature of the collected data. We hint cons and pros of each approach and discuss about possible communalities between the various approaches.