Task design to foster the competence in social decision-making on mathematics education

As society continues to progress, it is becoming more and more important to deal with issues mathematically, take risks and uncertainty into consideration, clarify the grounds in participating in judgements or decision-making, and make critical deliberations. This competence is defined as "decision-making”. We present the design of a task about saving more lives with automatic external defibrillators (AEDs), aimed at fostering this competency in mathematics lessons. In methodological terms, we use Lesson Study to carefully anticipate the process of students’ finding and solving problems. We review the design from different viewpoint, such as “What times and how should all the students in the class study?” or “When and what kind of materials should be presented?”