Calculate Expected Flips for Heads-Tails Sequence
Company: Yahoo
Role: Data Scientist
Category: Statistics & Math
Difficulty: easy
Interview Round: Technical Screen
##### Scenario
Product manager asks a quick probability check during a design review to gauge statistical intuition.
##### Question
You flip a fair coin repeatedly until the sequence Heads–Tails (HT) appears consecutively. What is the expected number of flips required?
##### Hints
Model as states: start, last flip H, and absorbing HT; use expected value equations.
Quick Answer: This question evaluates a candidate's proficiency in probability theory and stochastic-process reasoning, including Markov-style state modeling and expected-value analysis for stopping times.