QuantDojo vs Probability Paradox Lab

QuantDojo is the only app built specifically for quant finance interview prep. 1,300+ brain teasers and growing, covering every question type you'll face at top firms. WHAT YOU GET • 1,300+ brain teasers across Probability, Statistics, Combinatorics, Logic, and Game Theory • Questions tagged by firm — Jane Street, Citadel, Two Sigma, DE Shaw, Optiver, SIG, HRT, IMC, and more • 3 progressive hints per question to guide your thinking • Full step-by-step solutions with mathematical explanations • Spaced repetition to lock in what you've learned • Track your accuracy by category and difficulty HOW IT WORKS Pick a category, difficulty, or target firm and start solving. Reveal hints when you're stuck. Check the full solution when you're ready. Mark questions as solved or send them to your review queue. QuantDojo tracks your weak spots and resurfaces questions at the right intervals. WHO IT'S FOR • Students prepping for quant interviews • Career switchers moving into quant finance • Working professionals staying sharp PRICING Subscribe monthly or annually, or get lifetime access with a single purchase. Free users can preview 3 full solutions before subscribing. Privacy: All your data stays on your device. We collect nothing. Terms of Use: https://elilindt.github.io/quantdojo-site/terms.html Privacy Policy: https://elilindt.github.io/quantdojo-site/privacy.html

"With 23 people in a class, what's the chance two share a birthday?" The answer exceeds 50%. Were you surprised? Probability Paradox Lab is an interactive app that lets you experience mathematical paradoxes through simulation — results that feel wrong, yet are mathematically proven. [ HOW IT WORKS ] 1. Make your intuitive guess 2. Run the simulation and see the real result 3. Read the math explanation and understand why Be surprised by the answer. Be surprised again by the explanation. [ FREE THEMES ] Birthday Problem (Free) With just 23 people, the probability of a shared birthday exceeds 50%. Why? Monty Hall Problem (Free) After the host opens a losing door, switching wins 2/3 of the time. Mathematically proven — yet deeply counterintuitive. Two Envelopes Problem (Free) A seemingly valid argument says you should always switch envelopes. Where's the flaw? Coupon Collector Problem (Free) Collecting all 10 kinds takes about 29 pulls on average. Fast at first, then it stalls. [ PREMIUM THEMES ] One-time purchase unlocks 12 more paradoxes and Quiz Mode across all themes. No subscriptions, no ads for premium users. Ellsberg Paradox Why do people prefer known odds over unknown ones — even when the math says they're equal? Boy or Girl Paradox "One child is a boy." How does that single fact change the probability? False Positive Paradox A 99%-accurate test says positive for a disease 1% of people have. You're sick with only ~50% odds. Gambler's Fallacy Five heads in a row. Is tails due? Randomness is clumpier than it looks. St. Petersburg Paradox Expected value is infinite, yet you'd pay little to play. Why? Nontransitive Dice (Efron-style) A beats B, B beats C, C beats A. No die is the strongest. Parrondo's Paradox Two losing games, played in alternation, somehow become a winning strategy. Simpson's Paradox A treatment wins in every subgroup — yet loses overall. How? Secretary Problem Interview one at a time with no going back. The optimal strategy for catching the best. Benford's Law About 30% of naturally occurring numbers start with a 1. A curious statistical bias. Friendship Paradox Your friends have more friends than you — the network bias that makes it true. 100 Prisoners Problem If even one fails, all are executed. Yet one strategy saves everyone about 31% of the time. [ PERFECT FOR ] - Math & statistics enthusiasts - Curious minds who love "why?" - Brain teaser & trivia fans - Students and lifelong learners