Joint activity, or interaction, can be the basis for understanding how language use organizes both social activity as well as individual thought. These interactions can be a useful unit of analysis for studying how students use language to make sense of mathematical concepts and how students learn to appropriate specific mathematical language practices. These interactions are structured, although not determined by, the tasks which students are assigned. Establishing links between task design and mathematical language practices would allow us to build on connections between mathematical language practices and learning to draw conclusions about the relationships between task design and learning. In this study, I qualitatively analyze the design features of a set of tasks and some mathematical language practices of students engaging in them. I then employ a computational language model to extrapolate from my qualitative analysis of language practices to a larger corpus of transcripts. This allows me to observe how different students used mathematical language practices while working on the same task across different groups, classrooms, and schools. Findings suggest, when accounting for the influence of teachers, certain task design features are associated with differences in student discourse. I hope this project contributes to ongoing research on task design, language-responsive pedagogy, and methodologies that can expand what is possible with qualitative analysis of mathematical discourse. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]