The effect of class size on student learning has numerous policy implications and has been a major subject of conversation and research for decades. Despite this, few studies have been done on class size in the context of university settings or physics courses. This dissertation helps address that gap in the literature by quantitatively analyzing the effect of class size on students’ understanding of physics concepts in active-learning based introductory physics courses for bioscience majors at a large, R1 university. In the process, this dissertation also discusses the reasoning and methods behind three-level basic Hierarchical Linear Modeling (HLM), which is a particular form of statistical regression, along with analyzing the effects of several additional, non-class-size related, student and class-level characteristics on student understanding of physics concepts.

In this study, a student taking a given course is part of a section which is itself part of a larger Lecture. It was found that Grades, which were used as a proxy for students’ understanding of physics, varied a lot between individual students and also between Lectures, but varied relatively little between different sections within the same Lecture. Furthermore, these Grades were affected substantially by the student-level factors which were part of this study, including academic factors like GPA and repeating a course, as well as demographic factors like race and ethnicity. These Grades were also impacted greatly by Lecture-level factors that were part of this study, like academic term and Lecture instructor. However, these Grades were not consistently impacted by any of the section-level factors that were part of this study, including start times and mean GPA.

On class size specifically, within the ranges studied here, class size did not have much of an effect on Grades in the courses that were part of this study. There were some signs that larger Lecture sizes lead to lower Grades, but there was not enough evidence to be definitive, and there were no consistent trends in the impact that section size had on Grades. However, the relatively low variation in Grades between sections, together with a variety of other questions, issues, and limitations, means that this study is certainly not the end of the story. In particular, there are still open questions around the nature and meaning of Grades, as well as how class size and other student and class-level characteristics impact non-Grade related aspects of student, as well as teacher, well-being and success. There is still much work to be done and plenty of discussions to be had, both theoretically and empirically, when it comes to the types of courses that were part of this study and the factors that affect student understanding of the material covered by these courses.