J'ai postulé en ligne. J'ai passé un entretien chez Jane Street en août 2024
Entretien
30 minute first round consisting of around 3 scenarios, in total you'll probably have ~10 questions in total you'll be answering among those 3 scenarios, some smaller and simpler to verify that you know easy math, and some more complicated that involve deciding on a strategy or optimal choice. A recruiter will reach out to you to schedule, and then a trader will call your phone at the scheduled time.
I was first given 2 relatively simple scenarios for which I got all the questions right pretty quickly after asking for clarification on one of them. We then had 15 minutes left, and so they asked me about a betting game that was more difficult and I spent 30 minutes getting through his questions (we went almost 15 minutes overtime) and I was invited directly to the third round, so it looks like they asked me harder second round interview questions compressed into my first interview and were impressed. I'm also impressed with the difficulty of these questions even when the scenarios are simple enough, honestly requiring a mix of quantitative and qualitative intuition that you must quickly retrieve AND communicate clearly.
Questions d'entretien [1]
Question 1
You and your friend play a betting game where you start with 1 dollar and your friend starts with N dollars, where N is a natural number. Each round, you 'flip a fair coin for the shortest current stack' (e.g. you win the 'shortest stack amount' from your friend if it lands Heads and your friend wins the 'shortest stack amount' from you if it lands Tails).
You buy back in for an extra $1 every time you lose your current stack to your friend and the game continues, but if your friend loses all of his stack to you, he doesn't buy back in and the game ends.
(a) What is the expected number of rounds that this game will last?
(b) What is the expected amount of profit that you walk away with?
(c) What's the expected amount of times you expect to buy back in for an iteration of the game for very large N?
(d) In the real world, a U.S. penny has a ~51% chance of landing the same side-up it was before it was flipped up into the air, but an ~80% chance of landing Tails if it's spun from its edge on a tabletop. So, let's change the game from now on so you can also use your real-life U.S. penny instead (if it somehow lands on its edge, just flip/spin it again): you either flip the coin with the Heads side initially facing up (51% Heads), or with the Tails side initially facing up (49% Heads), or you can spin it on a tabletop (20% Heads). Or, you can stick with your perfectly fair 50% Heads coin whenever too.
Your objective is always to maximize your expected profit. What is your optimal strategy, and what is the expected amount of profit that you walk away with?
(e) The game also ends when have lost N dollars yourself (you lose when you're down N dollars from your original 1 dollar buy-in), in which case your friend wins. What is the minimum probability of landing Heads that the coin must have for you and your friend to have equal chances of winning the game?
There was a few phone interviews that involved probability and game theory questions. Before a final round interview in hong kong. Interviewers are very nice best to describe your thought process
Questions d'entretien [1]
Question 1
They asked me probability and gamer theory questions.
J'ai passé un entretien chez Jane Street (Londres, Angleterre)
Entretien
Interviewed for two rounds. I passed the first round last year so was able to continue immediately with the second this year. Probability/game theory questions. The interviewers are friendly and helpful.
Questions d'entretien [1]
Question 1
If you roll a dice and receive that amount in dollars but have the option of rerolling up to two times, how much would you like to pay to play this game?
J'ai passé un entretien chez Jane Street (Londres, Angleterre)
Entretien
Jane Street’s interview process is fast-paced, multi-round (But if you have a deadline they will react accordingly) , and deeply quantitative: mental math, probability puzzles, game theory..., and conversational talk just before you start doing the problems
Questions d'entretien [1]
Question 1
Some basic probability questions (more like brainteasers) involving expected values and markov chains. You should brush up on the greenbook and be comfortable with n-sided dice and strategies involving dice in general.