You must pass the online test before moving on to the next step. It is not extremely difficult, but you have to possess good knowledge of probabablity, statistics, & quantitative. You have 1 to 15 minutes to answer a question depending on the difficulty, thus you must be able to solve the probably immediately, no time to research online. Given the time constraint, the difficult part is that you MUST use math on a regular basis & remember which formulas to use. That was my problem, haven't used these tools for quite some time. I was pretty good at Math (top 1% for SAT & GRE), but I didn't pass the online test :-( The interview could have been more well-rounded by giving the candidates more chance to present their capabilities beyond the online test result.

There are some probability questions which is quite difficult. But you really do not need to solve to the end. They just want to test the way you think and solveproblems.