Jane Street · Trading interview skills · Outcry timed mock
Jane Street quant finance and trading: interview practice mock
Quantitative trading interview preparation: probability and conditioning, expected value and optimal decisions, then pricing and adverse selection. The topics follow Jane Street’s public resources; Outcry sets the questions, clock and scoring.
Format
- 3 sections · 18 items · about 45 minutes
- Format and scoring below apply to this Outcry mock. See the source check for verified firm details and practice adaptations.
- Negative marking on Probability, counting & conditioning, Expected value & optimal decisions, Market making & adverse selection: +1 correct, −1 wrong, −0.25 per skip or unanswered item, including timeouts (Outcry mock rule). Any item-specific mark weight is shown on the question.
- No going back in this mock. Answer or skip, and the next item loads.
- Questions are generated from Outcry's own banks; a retake changes the selection or parameters.
Sections
- Probability, counting & conditioning - 6 items, 15 minutes, 1 mark lost per wrong answer, 0.25 mark lost per skip or unanswered item. 6 items in 15 minutes. Conditional probability, Bayes, independent trials and counting. Identify the sample space before calculating.
- Expected value & optimal decisions - 6 items, 15 minutes, 1 mark lost per wrong answer, 0.25 mark lost per skip or unanswered item. 6 items in 15 minutes. Price random payoffs, use linearity and compare stopping or rerolling choices.
- Market making & adverse selection - 6 items, 15 minutes, 1 mark lost per wrong answer, 0.25 mark lost per skip or unanswered item. 6 items in 15 minutes. Two-sided quotes, expected edge, information in order flow and inventory costs. Every model states its rules.
A trading mock, separate from Strategy and Product
This paper prepares quantitative trading interview skills. The existing Strategy and Product assessment remains available separately; its business and product questions are not substituted for trading preparation.
Jane Street’s public trading interview guidance describes conversations with traders. Its Probability & Markets guide covers the foundations used to choose these three sections. The question counts, time limits and marks here are Outcry’s practice choices.
What to practise in each section
Start by defining equally likely outcomes and updating the sample space when new information arrives. Then work with expected payoffs and make decisions by comparing their conditional values. In the markets section, connect those values to bids, asks, costs and information in the counterparty’s trade.
No question requires you to arrive knowing option jargon. Read each stated toy-market rule carefully. A positive expected profit can still lose on a particular outcome; a paired or converted payoff is riskless only if the stated exposures cancel.
Use the score as feedback on your method
Explain your reasoning aloud and keep written working while you sit the mock. Afterward, use the marked script to check setup, calculation and decision errors separately. A correct number without a clear argument is incomplete interview practice.
The runner can mark numbers and choices, but it cannot replicate the back-and-forth of a trading interview. Use Jane Street’s public mock interview to practise responding to changed assumptions and feedback.
Section by section, with a worked example
Every example below is generated by Outcry, drawn from the same generator that section runs during the timed sitting. None of it is Jane Street's own material.
A. Probability, counting & conditioning
6 items in 15 minutes. Conditional probability, Bayes, independent trials and counting. Identify the sample space before calculating.
In this Outcry section: 6 items in 15 minutes, averaging 150 seconds per item. Each wrong answer loses 1 mark. Each skipped or unanswered item, including a timeout, loses 0.25 mark. Correct-answer weights are shown on the questions. These are the mock’s rules.
Example 1
A desk shows 10 quotes, each hit independently with probability 30%. What is the probability that exactly 5 of them are hit? Percentage to one decimal place.
Answer 10.3
Binomial: C(10,5) x 0.3^5 x 0.7^5 = 252 x 0.00243 x 0.168 = 10.3%. The C(10,5) counts which quotes were the ones hit.
Example 2
A crate holds 3 red-tagged units and 4 blue-tagged units. 4 are pulled out at random without replacement. What is the probability that exactly 1 of them are red-tagged? Three decimal places.
Answer 0.343
Hypergeometric: C(3,1) x C(4,3) / C(7,4) = 3 x 4 / 35 = 0.343. Without replacement means counting subsets, not multiplying independent draws.
B. Expected value & optimal decisions
6 items in 15 minutes. Price random payoffs, use linearity and compare stopping or rerolling choices.
In this Outcry section: 6 items in 15 minutes, averaging 150 seconds per item. Each wrong answer loses 1 mark. Each skipped or unanswered item, including a timeout, loses 0.25 mark. Correct-answer weights are shown on the questions. These are the mock’s rules.
Example 1
A box holds 25 tickets numbered 1 to 25. You draw 4 of them without replacement. What is the expected total of the 4 numbers? One decimal place.
Answer 52
Linearity again, and it does not care that the draws are dependent. Each single draw is a uniform pick from 1 to 25, worth (1 + 25)/2 = 13, so 4 draws are worth 4 x 13 = 52.
Example 2
4 fair 8-sided dice are rolled together. What is the expected value of the highest number showing? Three decimal places.
Answer 6.858
P(max <= v) = (v/8)^4, so P(max = v) is that minus the same at v - 1. Summing v x P(max = v) over v = 1 to 8 gives 6.858. The tail form E[max] = sum over v of (1 - (v/8)^4) gets there faster.
C. Market making & adverse selection
6 items in 15 minutes. Two-sided quotes, expected edge, information in order flow and inventory costs. Every model states its rules.
In this Outcry section: 6 items in 15 minutes, averaging 150 seconds per item. Each wrong answer loses 1 mark. Each skipped or unanswered item, including a timeout, loses 0.25 mark. Correct-answer weights are shown on the questions. These are the mock’s rules.
Example 1
Fair value is 157. You sell 50 lots at 163. What is the theoretical edge?
Answer 300
163 - 157 = 6 per lot, times 50 = 300.
Example 2
You end the session holding 0 unit(s) of inventory. Closing out costs 0.5 ticks per unit (crossing the spread to trade out). What's your total flatten cost, in ticks?
Answer 0
Flatten cost = |inventory| × cost per unit = 0 × 0.5 = +0 ticks. Carrying a position into the close isn't free - it's a real reason to trade back toward flat before time runs out.
Common questions
- Is this Jane Street’s real quantitative trading test?
- No. It is Outcry’s practice mock for topics in the firm’s public Probability & Markets guide. Jane Street describes conversational trading interviews rather than this fixed online paper.
- How is the quant trading mock different from Strategy and Product?
- This mock focuses on probability, expected payoffs, optimal decisions and markets. Strategy and Product remains a separate assessment focused on business, data and product reasoning.
- How long is this Outcry trading mock?
- 45 minutes: six generated questions in each of three 15-minute sections. These are practice settings, not a claimed Jane Street test duration.
- What marking does the trading mock use?
- Outcry awards +1 correct and deducts 1 for a wrong answer or 0.25 for a skip or unanswered item, including timeouts. This is our practice rule, not a published Jane Street marking scheme.
- Do I need prior finance knowledge for these questions?
- No. The market questions supply their payoff and trading rules. Practise interpreting those rules and explaining how probability and expected value support a decision.
Jane Street: official trading interview guidanceJane Street: Probability & Markets guidePractise probability separatelyPractise market making separatelySeparate Strategy and Product mock
Outcry is not affiliated with Jane Street. This mock practises publicly described interview topics using our own questions, clocks and marking; it is not the firm's assessment.