Online Test : About 40 problems. Mainly about probability and algorithm.
Phone interview : 4 times total. About 1 hour each. Asked about probability, algorithm, and financial open-end questions.
Final-interview : Based on resume.
Application process took a month since i have submitted my cv through the website.
The first part (for me it was also the last one), consisted of an on-campus test on probability & statistics, brainteasers, calculus and linear algebra. Though the problems didn't require tons of knowledge -- one will be competetive for the test having a decent knowledge of calculus (both 1-variable and multivariable, integrals, limits, double integrals, basic odes), linear algebra (characteristic polynomials, ranks, e.t.c.), probability and statistics (coins, bayes rule, normal distributions, medians/e.t.c.), the time limit is extremely brutal and will not let think about the problem too much. Surprisingly, there were almost no programming/algorithms questions (maybe 2 or 3 out of 80).
A good preparation would be the GRE subject test in mathematics sample papers (accomplished within the time limit, of course)
Interview questions [3]
Question 1
What is the complexity of the Quick Sort algorithm?
I applied through a recruiter. I interviewed at WorldQuant
Interview
I did two online test. About 3 hours for both. There is a broad range of subjects including geometry, integrals, probability, logic, statistics, complexity and sometimes a combination of those.
Interview questions [1]
Question 1
Consider a random permutations of numbers 1,...,31415. Let A be the number of it's fixed points. Let B be the number of non-fixed points. What is the variance of B-A?