The Market Making Game Interview: How to Answer 'Make Me a Market'

A scripted walkthrough of spread setting, inventory management, and adverse selection — the way Optiver, SIG, and DRW actually grade it.

Updated July 3, 2026 · QuantVault

At some point in almost every trading interview, the interviewer leans back and says: "Make me a market on X." X might be the sum of three dice, the number of piano tuners in Chicago, or the temperature in Sydney tomorrow. Whatever it is, this is the market making game, and it is graded on process, not on whether your number is right. Firms like Optiver, SIG, and DRW use it because it compresses the entire trading job into ten minutes: estimate a value under uncertainty, quote two-sided prices, manage the position you accumulate, and figure out when your counterparty knows more than you do.

What "make me a market" actually means

You must state two prices: a bid (where you buy) and an ask (where you sell), usually with a size. The interviewer then trades against you — "I buy," "I sell," sometimes repeatedly — and watches how you respond. There are four dials you control, and a good answer touches all of them explicitly:

Fair value: your best estimate of $E[X]$, stated with reasoning.
Spread: how far your bid and ask sit from fair value — wider when your uncertainty ($\sigma$) is higher or the counterparty may be informed.
Size: how much you are willing to trade at those prices. Small size when uncertain.
Skew: after a trade, shift both quotes in the direction of the flow to manage inventory and account for the information in the trade itself.

Estimating fair value often reduces to a quick expected value calculation, or a Fermi estimate with a confidence interval when the quantity is a real-world unknown.

Worked example: a market on the sum of three dice

Suppose the interviewer says: "Make me a market on the sum of three fair dice."

Step 1 — fair value. Each die has mean $3.5$, so $$E[S] = 3 \times 3.5 = 10.5.$$ The variance of one die is $\frac{35}{12}$, so $$\mathrm{Var}(S) = 3 \times \tfrac{35}{12} = 8.75, \qquad \sigma \approx 2.96.$$

Step 2 — quote. Say it out loud: "Fair value is 10.5 with a standard deviation of about 3, so I'm 9.5 bid at 11.5, one lot." A spread of 2 around a known distribution is defensible; if the payoff were something you could only estimate roughly, you would quote wider. If the interviewer trades randomly, each round trip captures the full spread — your expected edge is $1.0$ per side, since you buy $1$ below fair and sell $1$ above it.

Step 3 — react to flow. The interviewer buys. You are now short one lot at 11.5. Two forces say move your quotes up: you want to attract a seller to flatten your inventory, and the buy itself is weak evidence the buyer thinks the sum is high. So you skew: 10 bid at 12. If they buy again, skew harder and widen: 10.5 at 13, and consider cutting size.

Step 4 — handle the information shock. The interviewer now reveals that one die already landed on 6. New fair value: $$E[S \mid d_1 = 6] = 6 + 2 \times 3.5 = 13.$$ Your earlier sale at 11.5 is now expected to lose $13 - 11.5 = 1.5$ per lot. Don't freeze — re-center immediately (say 12 bid at 14) and buy back your short near the new fair value rather than hoping the dice bail you out.

Event	Your quote (bid / ask)	Position	Reasoning
Open	9.5 / 11.5	Flat	Symmetric around fair value 10.5
Interviewer buys	10 / 12	Short 1	Skew up: inventory + information
Interviewer buys again	10.5 / 13	Short 2	Skew harder, widen, reduce size
Die revealed: 6	12 / 14	Short 2	New fair 13; buy back near fair

The traps that fail candidates

Quoting too tight to look confident. A 0.5-wide market on a quantity with $\sigma \approx 3$ signals you don't connect spread to uncertainty.
Never moving your market. If the interviewer lifts your offer three times and your quotes haven't budged, you are the free option. This is textbook adverse selection: informed flow trades against stale quotes.
Moving the midpoint but not the spread. When you suspect informed flow, widen and skew — and trade smaller.
Ignoring inventory. Ending the game short five lots of something you think is going up means you managed price but not position. Sizing under uncertainty is exactly the logic behind the Kelly criterion: edge divided by variance, not bravado.
Anchoring on your first estimate. New information (a revealed die, a strange trade) should move your fair value mechanically, not grudgingly.

How to sound calibrated, not scripted

Narrate your reasoning at every step: state fair value, state uncertainty, justify the spread, and announce why you're skewing after each trade. Interviewers at market-making firms are listening for the vocabulary of the job — edge, inventory, adverse selection — used correctly and unpretentiously. If you don't know the answer to an estimation prompt, say what your 90% confidence interval is and quote wide around it; honest wide markets beat falsely precise tight ones every time.

The only real preparation is repetitions against an opponent that punishes stale quotes. Play our Make a Market game, which simulates exactly this interview with informed and uninformed flow, then try the betting game for sizing instincts and browse the full set of trading games to drill the rest of the loop.

Frequently asked questions

What is the 'make me a market' interview question?

The interviewer asks you to quote a two-sided market — a bid and an ask with size — on some uncertain quantity, like the sum of three dice or the weight of a 747. They then trade against your quotes over several rounds and grade how you set your spread, manage inventory, and update on new information. Your process matters far more than whether your initial estimate is correct.

How wide should my spread be in a market making game?

Scale your spread to your uncertainty: the wider your confidence interval on fair value, the wider your quotes should be. For a known distribution like dice you can quote around one standard deviation or tighter; for a Fermi-style unknown you should quote much wider and in smaller size. A tight market on something you barely know is the classic way to get picked off.

What is adverse selection in the market making game?

Adverse selection is losing money because the people who choose to trade with you know more than you do. In the game, if the interviewer keeps buying and your quotes never move, they are likely trading on information and you are selling below true value each time. The correct response is to skew your quotes in the direction of the flow, widen your spread, and reduce your size.

Which firms ask market making games in interviews?

Options market makers and prop trading firms use it most heavily — Optiver, SIG, DRW, IMC, and similar firms make it a standard stage for trader roles. It typically appears in first-round trader interviews and again on superdays, often layered with follow-up rounds where the interviewer reveals partial information mid-game.

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