I have a finance question and i need help with it.

You have not been paying attention to the news today. A friend tells you that the S&P 500 index had one of its biggest one day moves in twenty years. It changed by 20%. But for some unknown reason, your friend did not tell you whether the S&P 500 index went up or down. What is your best guess on whether it rose or fell? Why? How would your answer change if instead an individual stock moved by 20% in a day instead of the index