Informal inferential reasoning.

Year 11 (15-year-old) students are not exposed to formal statistical inferential methods. Therefore, when drawing conclusions from data, their reasoning must be based mainly on looking at graph representations. This study investigates the type of reasoning that might develop students' informal inferential statistical reasoning towards a more formal level. A perspectives model is developed for a teacher's informal inferential reasoning from the comparison of boxplots. The model is then used to analyse her students' responses to an assessment task. The resultant analysis produced a conjectured hierarchical model for students' reasoning. The implications of the findings for instruction are discussed.