Coin Probability Interview Questions
Coin probability interview prep for streaks, stopping times, biased coins, independence, and expected flips.
Candidates practicing coin-flip patterns for quant interviews.
What coin questions test
Coin questions test independence, conditioning, recursion, and pattern waiting times. The setup looks simple, so the interviewer can quickly add biased coins, streaks, stopping rules, or hidden-state variants.
Concrete example
The expected flips to see heads then tails is not the same as the expected flips to see two heads. Pattern overlap matters. For HT, after a head you are close; after a tail you reset. State diagrams keep this straight.
How to practice
Draw states for streak and waiting-time problems. Use direct binomial counting for fixed-length questions, and recursion for questions that stop when a pattern appears. Then practice explaining why each state is complete.
Common mistakes
The common mistake is assuming every two-flip pattern has the same waiting time. Another is forgetting that a failed partial pattern may still leave useful progress. That is exactly why state definitions matter.
Practice the pattern
Use the LeetQuidity curriculum and calibration to turn this topic into a focused practice plan.