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Jane Street · Quant trader / software engineer · Quant Trader, new grad / intern

Probability & Expected Value (spoken)

Run by an actual quant trader

What they actually ask

The question shapes this round uses. Larpy does not read these out. It builds each one from your own resume, because the generic version is the one you have already rehearsed.

  • “Roll two six-sided dice. What's the probability the sum is 7? Now what about the sum being 10?”
  • “Draw two cards: probability both are face cards if you replace the first; probability both are clubs if you don't replace it.”
  • “Roll two dice. What's the probability the product is odd? What about three dice?”
  • “Flip a fair coin until the first heads. Expected number of flips? Now expected flips to see three heads in a row?”
  • “Flip three coins. Probability of exactly two heads given that at least one is a tail?”
  • “Expected value of a die roll given the outcome is at least 4? Given the outcome is prime?”

What this round is judged on

  • Approach the problem methodically · clean steps, not guesses
  • Communicate clearly · narrate your reasoning
  • Correct your mistakes · take hints and revise without defensiveness
  • Comfortable with numbers and logic · reason quantitatively, no esoteric theorems

Where this round sits

Jane Street’s published process. Lime marks the stage this round runs.

  1. 01
    Application
  2. 02
    Phone interviews (remote)this round
  3. 03
    In-person final round (onsite)
  4. 04
    Decision
What happens in each stage›
Application
Rolling basis, no deadline. No GPA or degree requirement; interns come from 70+ universities. Jane Street says you can expect to hear from a recruiter within a few days.
Phone interviews (remote)
One or more remote interviews to start. For trading these are conversational probability/logic and market conversations with an actual quant trader; for SWE they are live coding. The interviewer calls you (Zoom if connectivity is poor).
In-person final round (onsite)
The final stage is in person: multiple back-to-back interviews mixing probability, a market-making game, estimation, a light coding/data-analysis chat, and fit. Jane Street books and pays for travel and hotel; interviews run weekdays only, dress casual.
Decision
Jane Street says you should hear back within about a week after the final stage. Reapplication is explicitly allowed (recommended wait ~1 year).

Sources

Built from what Jane Street publishes about its own process and from real interview data. No leaked question lists. The questions you get are generated against your own resume, so they are not from anyone else's interview.

Sources last checked . Hiring loops change, so this date is the honest limit on everything above.

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