Jane Street Interview Question: Player A rolls 3 6-sided dice... | Glassdoor.co.uk

Interview Question

Trader Interview London, England

Player A rolls 3 6-sided dices. Player B rolls a 20-sided

  dice. The player with highest score wins. Which player do you wish to be?

Interview Answer

3 Answers


The two players are equally likely to win because their distribution have the same mean and are symmetric respect to that distribution.

Interview Candidate on 14 Nov 2018

The EV are both 10.5 but the variance is different so i would prefer the one with lower variance that is the 20 sided die.

Nick Leeson on 5 Dec 2018

I don't really see why you should consider variance, given that you either win or lose, so there's no variance in the prize if you win. Perhaps if the winner won their score you may then wish to do some mean-variance analysis.
As others have said, same mean and symmetric, so you should be indifferent to either coin.
A common follow-up here is to ask; what about if we include more players? (that have either the 3 d6s or a d20)

Anonymous on 1 Feb 2019

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