This is the capstone. Six lessons built the survival half of the quant toolkit — the part Kelly and Monte Carlo only gestured at. You learned that ruin is an absorbing barrier and that even a fair game bankrupts a finite purse; that expectancy combines win rate and payoff into one verdict while R-multiples put every trade on one ruler; that the risk-of-ruin formula decays exponentially in units of capital so capital, not edge alone, buys survival; that maximum drawdown is a right-skewed distribution with a brutal time-under-water cousin; that the order of returns is irrelevant without cashflows and destiny with them; and that Monte Carlo ruin curves plus the stop-loss identity turn all of it into an exact position size. No formula sheet, no hints, no take-backs: every answer locks the instant you submit, the wrong options are the exact traps that wipe out real accounts, and your score stays hidden until the end.
Big picture
Risk of Ruin — the whole ladder
- Risk of Ruin
- What ruin is
- Absorbing barrier you cannot trade back from
- Gambler's ruin: fair game, ruin = (b−a)/b
- Paradox: positive edge ≠ safe
- Expectancy & the edge
- E = p·W − (1−p)·L
- R-multiples normalize to risk
- Breakeven win rate = 1/(1+b)
- The risk-of-ruin formula
- Units of capital N = bankroll ÷ risk per bet
- RoR = (q/p)^N, exponential in N
- Drawdown risk ≈ x^(2/k − 1) in Kelly fraction k
- Drawdown distributions
- Max drawdown is right-skewed, not one number
- Recovery asymmetry: 50% loss needs 100% gain
- Time under water can end careers
- Sequencing risk
- No cashflows → order irrelevant (commutes)
- Cashflows → order is destiny
- Retirees fear early bad years; savers want them
- Monte Carlo & stops
- RoR ≈ ruined paths ÷ total paths
- Ruin curve has a knee; size left of it
- Position = (account × risk%) ÷ stop%
- What ruin is
How this exam works
This is a graded exam. Questions arrive one at a time. Once you submit an answer it is final — there is no going back, no second try, and a wrong answer simply fails that question. Your score stays hidden until the very end, where you need 70% to pass. Read every option before you commit.
What does 'ruin' mean in the risk-of-ruin sense?
Select an answer to continue.
Passed? Here's what you now own
You can define a ruin barrier honestly, compute and stress an edge with expectancy and R-multiples, read the risk-of-ruin formula and its exponential payoff to capital, think in drawdown distributions and time under water rather than single numbers, respect sequence-of-returns risk wherever cashflows live, and turn a simulated ruin curve plus a stop-loss into an exact, survivable position size. Most of all, you’ll never again confuse ‘this system has an edge’ with ‘this system is safe.’
That’s the survival toolkit, end to end — the discipline that lets a real edge actually pay off, because compounding only rewards the accounts that are still open. Size so a bad month is a flesh wound, not a funeral, and you get to keep playing the game long enough to win it.