The Difficulty Factors Approach to the Design of Lessons in Intelligent Tutor Curricula

We present an approach to designing intelligent tutoring systems, termed the Difficulty Factors Approach. In this approach, the designer investigates, at each iteration of the design cycle, which skills and concepts are difficult for students, and what factors underlie those difficulties. We show that this approach complements existing design principles, producing data that helps designers apply principles in context. We also show that by continuing to investigate student difficulties throughout the design process, it is possible to discover difficulty factors initially obscured by other difficulty factors. We give an example of the application of the Difficulty Factors Approach in the context of the development of a cognitive tutor lesson on scatterplots.