How presentation affects the difficulty of computational thinking tasks

This paper discusses how a few changes in some computational thinking tasks proposed during the Bebras challenge affected the solvers’ performance. After the 2016 challenge held in November in our country (Italy), we interviewed some participants on the difficulties they had faced and we modified some of the tasks accordingly. We then proposed the whole set of tasks, with some of them modified, to pupils who had not participated to the challenge in November and compared performances in the two sessions. Using Item Response Theory, we measured the change in the distribution of difficulty and discrimination of the modified tasks. On the basis of the obtained results, we tried to better understand the many factors which influenced the difference in performances, both in the conceptual and cognitive task content and in its presentation (text, images, layout).