Quant Interview Expected Value Drills
Focused expected value drills for quant interviews, covering direct EV, linearity, indicators, stopping rules, fair prices, and betting decisions.
Candidates weak on expected value, fair prices, betting games, and stopping rules.
Start with direct EV
Direct EV drills use small payoff tables where you multiply probability by payoff. The purpose is to keep units clear: expected payoff, expected profit, fair price, or decision value.
Drill linearity and indicators
Use expected counts, card hands, matching problems, and dice sums. The drill is recognizing when a messy enumeration can become a sum of simple expectations.
Add stopping rules
Practice rerolls, thresholds, and pattern waiting questions. Define the state, write the recurrence or comparison, and check whether the answer is a probability, payoff, or expected time.
Concrete drill set
A focused block can include two direct EV questions, two indicator-variable questions, one stopping rule, and one betting decision where you discuss price, variance, and size.
Make decisions explicit
After each EV answer, ask what the fair price is and whether you would take the bet. This connects math to trading judgment and prevents a formula-only answer.
Common mistakes
Candidates often stop at positive EV, ignore variance, or enumerate when linearity would solve the problem. Drills should train method choice, not just arithmetic.
Practice the pattern
Use the LeetQuidity curriculum and calibration to turn this topic into a focused practice plan.