Developing meaningful educational assessments in massive open online courses can be a significant challenge for course developers. In this report, we discuss a variety of strategies that we have used in Materials Science and Engineering MOOC development in order to assure that we are giving our students meaningful and rigorous assessment activities. In particular, this report analyzes and compares short answer quizzes that are self-graded and those that are peer-graded. The analysis highlights the important of careful construction and continuous revision of grading rubrics.