Before the interview, I was sent a maths test (8 questions in 30 minutes), which were mostly probability, statistics and expected value type questions. After passing, you are invited to book a phone interview.
My interviewer was a software developer (at DRW, software developers and quantitative traders work very closely together). After a very brief introduction from the interviewer and myself, they started asking maths questions.
The first was an expected value question: you are given an envelope with a sum of money. You are given another, which either has £0, or twice the sum of money in the original envelope, with equal probability of each. Which do you choose to maximise your gain?
This was followed up by giving various values for which the first envelope would contain, but fundamentally the answer is the same: the expected value of both envelopes are identical. They then asked when you might choose the first envelope over the second, which opens up conversations about risk tolerance (you might want to “play it safe”, or might be risk-seeking and want to gamble) and how many times you get to play the game.
Another question was to estimate Earth’s population in 100 years time, to within a 90% confidence interval (i.e. you give a lower and upper bound, and you are 90% confident that your guess is correct). The interviewer wanted me to speak as I came to a solution, with the question designed to test your analytical skills and see if you have a reasonable and logical method to come up with a solution. In this case, I approached the problem by using Earth’s population today, and estimating the rate at which it is growing and how this rate might change, and the interviewer seemed happy.
There was a stochastic process based question, which involved a little maths, and I was also given a string of numbers and asked to find the pattern (in terms of n, e.g. n^3 or 3n + 2). The main takeaway was to speak your thought process out loud, as even where I was struggling with the maths questions, the interviewer wanted to know my approach and how I thought about the question, asked why I decided to approach the problems the way that I did, etc.
They were also very quick to move through the application process, from submitting, to maths test progression, to response after the 1st round interview, after which I was rejected and did not progress further. Unfortunately, they do not provide any feedback, but this seems to be standard across firms, and the rest of the application process and interview was a positive experience with a friendly interviewer.