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Quant Trader

Quant Trader

The night before

Read it tonight, then once more on the way in.

Back to the rounds

1The day

  1. Online testQuick sums and number sequences against the clock, often multiple choice with a point lost for each wrong answer.
  2. Phone roundProbability and expected value, worked out loud with a trader.
  3. Making a marketYou give a price to buy and a price to sell something uncertain, they trade with you, and you adjust.
  4. Betting gamesGames where you decide whether to play, how much to bet and when to stop, plus quick estimates.
  5. The final chatA longer problem where how you reason matters as much as the answer, and why you want to trade.

2How to answer

Make a market15 min

  1. Fair value out loud3 min
  2. A width that pays for what you don't know2 min
  3. Size2 min
  4. Update after a trade or a reveal5 min
  5. Your position3 min

Solve a probability problem out loud15 min

  1. Restate1 min
  2. Try a small case3 min
  3. Choose the method2 min
  4. Compute5 min
  5. Sanity check2 min
  6. Take the hint and the follow-up2 min

Tell a story from your work2 min

  1. The situation in one line15 sec
  2. What you did60 sec
  3. The result, with a number30 sec
  4. What you'd change15 sec

3Numbers to have ready

Say each answer out loud, then open the fold.

  • The 8-minute test: the pace for 80 in 8, and what a wrong answer costs.

    6 seconds a question. A wrong answer costs a point, so skip rather than guess. A score of 50 counts as test pace here.

  • One fair die: its expected value and variance.

    3.5, and 35/12, about 2.92. The standard deviation is about 1.71. Variance and risk

  • The total of two dice: expected value and standard deviation.

    7, and √(35/6), about 2.42. Variances add, so it isn't twice 1.71. Variance and risk

  • A die pays its face, and you may roll again once. When do you keep, and what's the game worth?

    Keep 4 or more. It's worth 4.25. Expected value

  • The Kelly stake on a coin that wins 60% of the time at even money.

    0.6 − 0.4 = 20% of your money. Betting games

  • You quote 6 at 8 on a die worth 7 to people who know no more than you. What do you make a trade?

    About 1, half your width of 2. Make a market on a number

4Traps

  • My market is 7 at 7.No gap means no expected profit and all of the risk. The spread is what pays you to stand there.
  • It's 36.A bare number, right or wrong, shows nothing. They're grading the route, so say it as you go.
  • We decided, we built it, and we fixed it.They're hiring you. With "we" all the way through, they can't tell what you did.
  • 1 at 12, to be safe.Nobody would ever trade on that. They want a market you'd really trade, with your reasons.

5On the day

  • Ask which AI tools, if any, you may use in each round.
  • Say your plan before you solve, so they can steer you early.
  • Stuck for a minute? Say what you've tried and ask for a hint. Taking one well counts.
  • Check units and sizes out loud before you give a number.
  • In a market, say your fair value before you quote, and keep your position in view.