This study investigated how pre-service middle school mathematics teachers attend, interpret, and respond to the students' thinking about statistical concepts in a case-based teacher training environment. 25 pre-service middle school mathematics teachers participated in the study, and they were asked to make evaluations on the cases given. Based on these evaluations, classroom discussions were held on student thinking, the reasons for students' difficulties, and how to overcome these difficulties. The discussions and evaluation reports were analyzed within the framework of professional noticing of children's mathematical thinking. The results showed that although the pre-service teachers could mostly attend to student thinking correctly, these identifications remained superficial. The pre-service teachers were mostly able to interpret student thinking in such a way as to indicate the state of understanding or misunderstanding. When the pre-service teachers' responding skills were examined, it was revealed that they mostly suggested approaches based on partial conceptual understanding to overcome students' difficulties. In addition, the results obtained from the study revealed that the pre-service teachers' noticing skills differed from one case to another.