PRACTICE GUIDE OLD MISSION
Old Mission Quantitative: what the test is, and how to train for it
The Old Mission quantitative screen is 25 questions in 35 minutes - about 84 seconds each - answered by picking one of the options. There is no negative marking, so leaving an item blank gains you nothing over guessing.
Where it sits: Quantitative section of the online test. The practice sitting on this page runs the same item count, the same clock and the same marking rule, with questions generated by Outcry rather than taken from Old Mission.
Outcry is not affiliated with Old Mission and has no access to their assessment content. This guide describes an assessment format that candidates report publicly; the questions here are generated by Outcry and are not Old Mission’s own.
What it screens
A Chicago-based options market maker and hedging firm trading listed derivatives across global exchanges.
- ✓Expected value computed fast and used to make a decision
- ✓Conditional probability and Bayes updates without formal notation
- ✓Ranking likelihoods rather than computing them exactly
- ✓Fermi estimation: decomposing an impossible question into three easy ones
Where it sits at Old Mission
This section does not arrive on its own. It opens the paper, and the sitting around it runs 60 minutes and 26 items in total, with Coding problem on the same continuous clock. Candidates who prepare only for this round tend to be caught by the pacing of the rest.
There is no going back. You answer or skip, and the next item loads, which means the decision to leave an item is final at the moment you make it.
The format
These are the numbers the Old Mission sitting on this site runs on, matching the format candidates report.
| Questions | 25 |
|---|---|
| Time | 35 minutes |
| Per question | 84 seconds |
| Negative marking | No |
| Answer style | Multiple choice |
| Where it sits | Quantitative section of the online test |
What it tests, with a worked example
Every example below is generated by Outcry, drawn from the same question generators the timed drills run. None of them is Old Mission’s.
Conditional probability
Bayes' rule in disguise: a test result, a signal, a drawn card, and what it implies.
Example
You have one fair six-sided die and need a uniform random number from 1 to 7. Which procedure works?
- Roll twice and take the larger, mod 7, plus 1
- Roll twice and take the sum mod 7, plus 1
- Roll once and multiply by 7/6, rounding
- Roll twice for 36 outcomes; re-roll on the last one, map the other 35 into 7 groups of 5
Answer Roll twice for 36 outcomes; re-roll on the last one, map the other 35 into 7 groups of 5
36 outcomes can't split into 7 equal groups, but 35 can (7×5). Discard one outcome and re-roll - the sum-mod-7 trick fails because sums are not uniform.
Counting and combinatorics
Arrangements, selections and the complement trick that turns a hard count into an easy one.
Example
A counter sits on square 2 of a row numbered 0 to 12. Each tick it moves one square left or one square right with equal probability, and it stops on 0 or on 12. What is the probability it stops on 12?
- 5/6
- 1/7
- 1/6
- 1/2
Answer 1/6
The position itself is a martingale in a fair walk, so its expected stopping value equals its start: p x 12 + (1 - p) x 0 = 2, giving p = 2/12 = 1/6. Step size does not enter it.
Estimation under uncertainty
A number nobody knows exactly, reasoned to the right order of magnitude out loud.
Example
Whole numbers are picked one at a time, and you get to keep picking. How many do you have to pick to be certain that two of them leave the same remainder when divided by 18?
Answer 19
The remainders are the 18 boxes, 0 through 17. Picking 18 numbers can dodge a repeat exactly once, by hitting every remainder, so 19 forces one. The same statement says two of the picks differ by a multiple of 18, which is how this argument usually turns up.
Ranking outcomes
Ordering several events by likelihood, where only the exact order scores.
Example
Stock Price FOXTROT $192.99 CEDAR $275.93 INDIGO $229.45 GAMMA $78.63 ALFA $177.05
The index above is price weighted with a divisor of 4.7703. GAMMA at $78.63 is replaced by ECHO at $243.00. What is the new divisor?
Answer 5.5922
The index level cannot jump on a corporate action, because nobody's wealth changed. Before: the prices sum to $954.05 and the level is $954.05 / 4.7703 = 199.9979. After: the prices sum to $1,118.42. Set the new divisor so the level is unchanged: D_new = $1,118.42 / 199.9979 = 5.592159. Equivalently D_new = D_old x (new sum / old sum) = 4.7703 x 1.172287. Leaving the divisor alone would print a level of 234.4549, a move of 17.229% that no holder experienced. This is exactly how the Dow divisor drifted from 1 to well under 0.2.
Waiting times and repeated trials
How long until the first success, and why the answer is rarely the average you expected.
Example
A trading floor has 40 people on it. What is the chance that at least two share a birthday, as a percentage?
Answer 89
There are C(40,2) = 780 pairs, each matching with probability 1/365. P(none) ≈ e^−2.14 ≈ 0.12, so about 88%.
Reading the question exactly
At least, exactly, and given that - the three phrases that change the answer entirely.
Example
A price rises 58% in one quarter and then falls 40% in the next. What is the net change over the two quarters?
- -5.2%
- 18%
- -23.2%
- -18%
Answer -5.2%
100 goes to 158, then loses 40% of 158, landing at 94.8. Net -5.2%. The naive answer 18% misses the cross term, which is -23.2%.
What a good score looks like
On a paper of 25 questions with no penalty for a wrong answer, the only thing an unanswered question can do is cost you. Probability rounds are usually marked as part of a wider battery, so a standalone threshold is rarely reported. Where candidates do describe one it clusters around getting two thirds of the items right, with the caveat that these sections are short enough that two mistakes move you a long way.
How to train for it
- 01Practise setting up before calculating. Most wrong answers on these are a correct calculation of the wrong quantity.
- 02Do them timed. A probability question you can solve in four minutes and the paper gives you ninety seconds for is a question you cannot solve.
- 03Work the complement first whenever the question says at least or at most. It is usually the shorter route and it is almost always the intended one.
TRAIN IT HERE
The drills that match each section
Likelihood Ranking
Order events from most to least likely - the exact screen-question format.
Fermi Estimation
Piano tuners in Chicago, atoms in a body - scored on order of magnitude.
Quitters Never Lose
A casino stopping-strategy game that is secretly a martingale lesson.
Tail Risk
Rare events and fat tails, and what they do to a plain expected-value estimate.
SIT THE FULL BATTERY
All the sections back to back on one clock, marked the way the real screen marks them, with a by-skill breakdown at the end. Included with any pass.
Also reported at Old Mission
Common questions
- Is the Old Mission quantitative test multiple choice?
- Multiple choice. You pick one option per question.
- How long is the Old Mission quantitative test?
- 25 questions in 35 minutes, which is about 84 seconds each.
- Is there negative marking on the Old Mission quantitative test?
- No. A wrong answer costs nothing beyond the mark you would have earned, so leaving an item blank is never better than guessing at it.
- How do I practise for it free?
- Every drill linked on this page is free to play, with no account, inside a daily run cap. Questions are generated fresh each run, so there is nothing to memorise between attempts. The full Old Mission Quant Screen sitting puts the sections back to back on one clock.