As industries relating to science, technology, engineering, and mathematics in America continue to grow, employers will need more mathematicians and mathematically able workers than are currently graduating. Women are an underrepresented portion of these graduates, and researches say that this could be due to the difference between women’s and men’s mathematical confidence. Calculus I is a required course for all STEM majors, and this course has proven to be a leaky point in the pipeline, a point at which women leave STEM degree programs at significantly higher rates than men. The purpose of this study is to explore what factors in Calculus I most affect the mathematical confidence of women in STEM-related majors. I share how I analyzed data that I collected during focus group interviews, and what patterns emerged in my analysis. I also offer an insight into the experiences of a few of my participants; these act as case studies. I explore how identity plays a key role in the experiences of these women enrolled in calculus I. Finally, I offer suggestions as to what universities and professors can do in their classrooms in order to improve the retention rates and experiences of women in their courses.