Abstract. While the number of contestants in the Dutch Olympiad in Informatics was declining, the number of participants in the Bebras contest grew rapidly. In order to reach these Bebras participants for joining the Olympiad, several steps were taken. We analyzed the differences between the contests. We offered Bebras contestants an introductory course in programming. And we changed he contest format of the first round of the Olympiad, introducing two new types of tasks. As a result, the number of contestants increased and girls returned to the Olympiad.

Predicting the difficulty level of a task on the concepts of computer science or computational thinking, like in the Bebras Challenge, proves to be really hard. But the announced difficulty level is needed in the contest format used in many local challenges. The Dutch contest system Cuttle has a new module for analysis. This is applied to one specific contest in order to find parameters explaining task difficulty. Using quantitative methods we were able to confirm a relation between answer types and difficulty and a tendency that tasks on data, data structures and representation are better answered than tasks on algorithms and programming.

Predicting the difficulty level of a task on the concepts of computer science or computational thinking, like in the Bebras Challenge, proves to be really hard. Question difficulty breaks down in content difficulty, stimulus difficulty and task difficulty. Several instruments are suggested to predict the overall difficulty level, like using a questionnaire or a rubric; these instruments are applied on the data of a recent contest and proved useful. Relative scoring could also turnout helpful. Especially on content difficulty easy applicable solutions are lacking.