Subjective elements in children's comparison of probabilities

In this research work we study the comparison of probabilities by 10-14 year-old pupils. We consider the different levels described in research about these tasks, though we incorporate subjective distractors, which change the predicted difficulty of some items. Analysis of students' arguments serves to determine their strategies, amongst which we identify the "equiprobability bias" and the "outcome approach". Analysis of response patterns by the same pupil serves to show that the coincidence between the difficulty level of probabilistic and proportional tasks is not complete and points to the existence of different types of probabilisitic reasoning for the same proportional reasoning level.