The student panel isn't an interview. It's just everyone being interviewed (~75 students) in an auditorium with a panel of about 6 current students. It's your opportunity to ask questions to the students that you wouldn't necessarily ask an admissions committee (night life, competitiveness, etc.). There is no one from the admissions committee in the room, so you are not judged in any way during the student panel. I actually liked this part of the interview; you can learn a lot from those students on whether or not pitt is a good fit for you.