Goldman Sachs Interview Question: Suppose that you have a fair ... | Glassdoor

Interview Question

Summer Internship - Quantitative Investment Strategies Interview(Student Candidate) New York, NY

Suppose that you have a fair coin. You start with $0. You

  win 1$ each time you get a head and loose $1 each time you get tails. Calculate the probability of getting $2 without getting below $0 at any time.

Interview Answer

5 Answers


Draw a tree to have an idea of how to compute the probability. The flips are all independent with each other.

Interview Candidate on Apr 10, 2012


Vipin Agrawal on Sep 2, 2013

Because if he requires 2 heads = $2, then it means he require HH out of {HH,HT ,TH,TT}
We cannot consider TT because it would turn to zero. Therefore, he has 1 chance out of 3. Hence 1/3.

Karan More on Jan 31, 2015

Each flip has a .5 possibility of being head.
(.5)(.5)=.25 or 1/4

Anonymous on Dec 21, 2016

Marchov chain with 2 and -1 absorbing OR geometric series 1/4^n from 1 to inf=1/3

Anonymous on Sep 18, 2017

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