The least biased and most useful sample for determining public opinion on whether hockey is too dangerous would be the group of shoppers at a shopping mall. This group is more likely to represent a diverse cross-section of the general public, including individuals who may or may not be fans of hockey, thus providing a broader perspective on the issue.
In contrast, fans at a football game or fans at a hockey game would be more likely to have strong opinions tied to their allegiance to specific sports, while a group of local sportscasters may have a professional bias towards promoting sports. Therefore, the shopping mall group would provide a more balanced view.