Going to start sharing questions commonly asked in quant finance interviews. If anyone has topics they'd particularly like to see covered, let me know. I'm a current quant with many years of experience in the industry.

Player A and Player B play a coin tossing game where the person who flips more heads wins. Player A gets to flip a fair coin 20 times while Player B gets to flip 21 times. What is the probability Player B wins the game?

A lot of great responses here and some did get the correct answer: Player B has a 50% chance of winning this game. Didn't see a lot of great explanations, so here's an elegant one via symmetry. If A only flips 20 times while B flips 21 times, B must end up with either more

A woman has two children. I tell you one of them is a girl. What is the probabily the other child is a boy?

67% (!) of people chose 1/2, which is wrong ☠️ Intution would say knowing one of the children is a girl doesn't impact the odds of the other child's gender. This is wrong. We can see it by enumerating all the possibilities of the genders of the two children. G - G B - G G - B

I have two envelopes. Inside one I put some amount of cash (say $X) and in the other I placed twice that amount ($2X). You can pick one envelope to keep. After you look inside, I give you the opportunity to switch envelopes if you’d like. Are you better off switching?

A group of people wants to find their average salary on the condition that no individual would be able to find out anyone else's salary. They have no way to communicate except by speaking to each other. Can they do this?

Given the a fair coin, what is the expected number of coin flips needed to get three heads in a row?

This gets an A+

What is the expected number of cards you need to draw to see an Ace in a normal 52-card deck?

Two random variables X and Y have correlation 0. Are X and Y necessarily independent?

How many trailing zeros are there at the end of 100! (100 factorial)

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Restarting my quant interview questions series, this time with a more stats focus than prob brainteasers. I have a univariate linear regression y ~ X*beta with 100 observations. I accidentally load my data twice so now I have 200 observations. How does the beta estimate change?

One more thing to file under “hedge funds don’t hedge”

The screenshot from the book are below. Remember that you can still download the draft at linktr.ee/paleologo. Pls repost so that all can rejoice in the pleasures of diversification. (6/n=6)

If anyone else was wondering why some of their features for predicting fair price of a sports market derived from Polymarket data were utterly useless…