This material is based upon work supported by the National Science Foundation Division of Research on Learning in Formal and Informal Settings under Grant #1258448. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

The authors are also grateful for the support of the MIT RELATE group, edX, and the 6.002x course team. The authors would also like to acknowledge the contributions of Yoav Bergner and Samuel Finegold, who assisted with development of the coding framework, and those of Deepa Vasudevan, who assisted with testing the framework.