I talked about an instance where one of my group member's calculations were obviously wrong. Nobody else in the group was going to say anything or question this member's work. The group member seemed very confident about his calculations. In a polite way, I spoke up and initiated a discussion with the group member. He began explaining his calculations and my responses were along the lines of, "My understanding of how to calculate this ratio is...let's look it up just to be sure." After some discussion, he realized that he had made some mistakes in his calculations. I demonstrated leadership by initiating a difficult conversation, which brought about a better result for the whole group.