Heavy on expected value and articulating your steps on the problem. You should review fundamental statistics and know how many cards are in a deck. In addition I would recommend the green book if you have time. Interviewers were very nice, however your performance boils down to how you did on the questions they gave.

Several phone calls to go to the final round. The phone calls consists of mathematical, probabilistic brain teasers which was not that hard for a mathematics major. Final round was to harsh for me, strong mentality is required