The topic of this research study is mastery learning, an educational theory that began with the work of John Carrol in 1963. The core principle of this theory is that all students can achieve uniform learning outcomes, but it will take some students longer than others to reach the same performance goals. The problem that this research study addressed is that college students in STEM courses where the traditional method of instruction is used often lack a feeling of deep understanding of the ideas being taught. The purpose of this quantitative causal-comparative study was to compare the traditional method of instruction with the mastery learning method of instruction. The theoretical framework for this study was based on the constructivist learning theory. The study used a quantitative methodology and a causal-comparative design to determine whether mastery learning has an impact on students' feeling of deep understanding of the ideas taught in a college calculus II course compared to the traditional method of instruction. A comparison was made using end of semester surveys to compare students' responses to the question of whether they feel as though their understanding of the ideas taught in the course were deepened by the instructional method used for the course. This study found a significant difference in feelings of deep understanding between students who received their instruction via the mastery learning method and the traditional method. These results build on existing evidence that allowing students multiple opportunities to demonstrate mastery regardless of how much time is needed to do so with timely feedback and assessment, can increase academic success in courses where the subject matter has been traditionally challenging for many students. Future research should examine the level of anxiety students feel when taking STEM courses compared to non-STEM courses and whether mastery learning has any effect on reducing that anxiety. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]