The research of psychologists, in particular from Kahneman and Tversky, has shown that in many situations of everyday life, people estimate the probability of random events using certain heuristics, specially representativeness. Much of the subsequent research in this area supports their thesis. Nevertheless, most of this work has used verbal problems as the means of studying people's conceptions and thinking, whether in a questionnaire or in an interview. In this work we present the results of a study of the pupils' use of representativeness in a situation of simulation of one of the classical problems related to the subject. The experience consisted of an individual interview with the students while simulating this situation and graphically representing the results, in order to answer some predetermined questions posed by the researcher. The analysis of student's pattern of responses before and after the realization of the simulation shows a wide variety of conceptions and the influence of the result of this simulation on the initial arguments of the pupils. As a result of this we conclude the didactical possibilities of simulation both as a means of exploring pupil's probabilistic intuitions and as an educational tool to overcome some of the misconceptions concerning these intuitions.