Issue with randomly draw questions from the question bank.

Hi,

Not sure if I am doing this right. I have a question bank with total of 8 questions. I would like to be able to draw 3 questions randomly from the question bank every time. I have the "Draw question randomly" checked, and also selected "3" from the "Include # questions" drop-down menu. But somehow the questions that appear were always the same. Any suggestions are welcome. Thanks in advance.