The preliminary round involved an excel sheet. There was information on the sheet and you had to work on excel to organize and analyze the data and then answer follow up questions. Having a good knowledge of excel makes this part easier. The first round was a phone interview that assesses critical thinking, and problem solving. They ask about approximations and probabilities dealing with confidence intervals. Work on walking someone through an approximation problem. Questions like "how many pennies are in NYC" is a good example.