Our goal is to provide current and future visitors to the edX Site with the best possible educational experience. To further this goal, we sometimes present different users with different versions of course materials and software. We do this to personalize the experience to the individual learner (to assess the learner’s level of ability and learning style, and present materials best suited to the learner), to improve our understanding of the learning process, and to evaluate and improve the effectiveness of our course materials, payment models, platform features, and offerings.