The purposes of this study were to investigate (a) undergraduate students' reasoning about the concepts of confidence intervals (b) undergraduate students' interactions with "well-designed" screencast videos on sampling distributions and confidence intervals, and (c) how screencast videos improve undergraduate students' reasoning ability concerning confidence intervals. The participants in this qualitative study were selected from the population of University of Virginia students who have taken Introduction to Statistical Analysis (STAT 212). The study included one initial interview session, one video orientation session, and one final interview session each lasting approximately one hour. During the interviews, participants will work through a set of nine tasks that attempt to assess students' statistical reasoning ability on the topic of confidence intervals. To control for potential learning during the initial interviews, three of the ten participants were selected to participate in the initial and final sessions but will not be given the opportunity to interact with the screencast videos. For each participant, an individual case study was written to provide detailed information about their initial reasoning about confidence intervals, their interactions with the screencast videos during the orientation session (for the half in the video group), and improvements in their reasoning identified during the final interview. In addition, a cross-case analysis was presented. The main finding was that even though undergraduate students who take a one semester introductory statistics course leave this course we a number of misconceptions about the concepts related to confidence intervals, the interaction with screencasts videos designed based on the principles of proper multi-media design, metacognitive learning, and multiple forms of representation can significantly enhance these students conceptual understanding of the confidence interval, especially the confidence interval's interpretation related to repeated sampling. These findings have implications for both statistics educators and learners. [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/en-US/products/dissertations/individuals.shtml.]