During a research project investigating understanding of variation students in a tertiary level introductory statistics course completed a questionnaire prior to, and at the end of, the course. This paper reports on interviews of selected students designed to determine whether more information could be gathered, and to identify those teaching and learning activities that assisted students to develop understanding. Prompting assisted students to develop better quality responses but cognitive conflict situations proved challenging. The diversity of activities identified by students as assisting development of understanding provides a challenge for educators in planning teaching sequences. Both educators and researchers need to listen to students to better understand the development of reasoning.