Teachers' Knowledge About Informal Line of Best Fit

The purpose of this study was to investigate teachers' subject matter knowledge relevant to the teaching of informal line of best fit. Task-based interviews were conducted with nineteen pre-service and in-service mathematics teachers. The results include descriptions and categorizations of teachers' conceptions, criteria for placement, accuracy of placement, and interpretation of the informal line of best fit. Implications regarding teacher preparation for the teaching of this topic, including current status and recommendations for future preparation, are discussed.