TreatmentsTwo independent variables, self-directed learning materials-presentation formats and self-directed learning approaches were manipulated across each treatment condition. There were two formats for presenting self-directed learning materials: the animation version (for CAEG) and the paper version (for PAG).To help participants develop number sense, seven self-directed learning units were designed for different types of self-directed learning. One activity from each unit was provided during each of the seven class periods. For the CAEG group, seven computer animated self-directed learning activities based on the lessons in the textbook used at the elementary school, were designed by the researchers and were number sense oriented (Griffin, 2004; Yang & Wu, 2010). These seven animated self-directed learning activities focused on conceptual or relational understanding. During the processes of animation activities, one example was presented through dynamic visualization, audio, interaction, and questions to lead students in learning number sense related concepts. Immediate feedbacks on students’ selections were presented on the screen. If student answers were incorrect, the screen showed “Your answer is incorrect, please try it again!” After the example, students were asked to take a quiz which includes several questions. The testing results were displayed to let the students know their performance. Take fraction comparison for example, one of the examples used for CAEG group is described as follows:A3. Speed eating activity for CAEG: Mary ate 8/9 of a cake and John ate 15/16 of the