PCK and average

This paper considers the responses of 26 teachers to items exploring their pedagogical content knowledge (PCK) about the concept of average. The items explored teachers' knowledge of average, their planning of a unit on average, and their understanding of students as learners in devising remediation for two student responses to a problem. Results indicated a wide range of performance and a wide range of ability in realtion to a hierarchical statistical PCK scale. Suggestions are made about developing teachers' PCK.