| Understanding of statistics is important and central to a democratic society. It helps to develop citizens, consumers, and workers that are productive and engaged critically and knowledgeably in the world around them. Statistical literacy has become primarily the responsibility of our schools. As a result, teachers need to know what and how to teach statistics. Unfortunately, few teachers have the specialized knowledge necessary to do so. While some research has identified the sense teachers make of statistics, there has been a lack of research of middle school teachers' content knowledge of variability. This study aimed to fill some of that gap by investigating a middle school teacher's content knowledge of variability in data distributions.;A qualitative study was undertaken with a middle school teacher during her academic school year. This study took a bidirectional view of studying teacher content knowledge---prior to and during teaching---including professional development sessions, lesson planning, performance tasks with an interview, and teaching a lesson. This approach differs from the typical education research on teacher knowledge that tended to focus on what teachers know either prior to or during teaching. In addition, in this study I used the construct of sensemaking, which includes the cognitive practices of noticing, interpreting, and implementing (Weick, 1995; Drake 2006) to study teacher knowledge as a dynamic phenomenon.;The findings of this study showed that there was a dynamic connection between teacher content knowledge exhibited prior to or during teaching, and a more complete snapshot of her content knowledge was attained. Teacher knowledge exhibited in one direction---prior to teaching---was either confirmed, extended, or not made visible during teaching. And in the other direction---during teaching---new content knowledge was exhibited that was not captured before.;The results of this study also attest to the value of using the construct of sensemaking to study teacher content knowledge as a dynamic phenomenon. Findings from this study demonstrated that the construct of sensemaking aligned with the bidirectional view of studying teacher content knowledge. Findings also indicated that the fruitfulness of the teacher's cognitive sensemaking practices---noticing, interpreting, and implementing---could affect the strength of the content knowledge that the teacher exhibits.;Although promising results were obtained regarding the use of this bidirectional approach and the construct of sensemaking---noticing, interpreting, and implementing---to study teacher content knowledge of variability, their usefulness and applicability are yet to be investigated in other statistics topics and other academic subjects. |
