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)

Screening -> Online tests in math (many problems on a variety of topics) and programming (3 easy problems on data parsing and filling in gaps) -> 3 technical interviews (math, programming, and DS/finance), usually a few simple warm-up questions and 2 more difficult problems to test the depth of knowledge -> interviews with teams, talk about your experience, scientific work, then questions related to the specifics of the team you are applying for, you need to come up with hypotheses about the data -> rejection