Hypothesis testing is a key concept included in many introductory statistics courses. Yet, due to common misunderstandings of both scientists and students, the use of hypothesis testing to interpret experimental data has received criticism. With statistics education on the rise, as well as an increasing number of students enrolling in introductory statistics courses each year, there is a need for research that investigates students’ understanding of hypothesis testing. This paper describes results obtained from a larger study designed to investigate introductory statistics students’ understanding of one population hypothesis testing. In particular, we present on one student’s understanding of the concepts involved in hypothesis testing, Steve, who provided us the best spectrum of different levels of knowledge according to APOS Theory, our guiding theoretical framework. Based on this data, we suggest implications for teaching.