This has ranged from using 5 problems per semester in a class of 22 groups with no peer tutors, to using 12 problems per semester in a class with 5 groups assisted by peer tutors. My current model is to divide the course into weekly topics, which are first presented by a lecture or discussion session. Each lecture day is followed by a problem day, in which groups of students must analyze a real life problem whose focus is an application of the weekly topic. Ten to twelve problems are completed each semester.
Assistance is provided by one or more peer tutors.
Students are accountable for individual work, but also for group work through problems and through group quizzes and exams.