The guiding idea "Data and Chance" represents one of the five content areas that are essential for mathematics education in lower secondary school and are binding nationwide due to educational standards. How can this guiding idea be brought to life? How can statistics and probability theory be connected to the single guiding idea of data and chance for schools? The book "Guiding Idea Data and Chance" for lower secondary education provides practical teaching and didactic-methodological answers to these questions. It starts from concrete teaching-relevant problems and unfolds the current issues of stochastic didactics based on them. Through viable examples, content-related and process-related standards for stochastics are interconnected to make real-life statistical phenomena tangible in the classroom.