Point72 Data Scientist Interview Experience — HackerRank OA With a Circle-Geometry Question, Then a Coin-Flip Expectation Puzzle

OA

60-minute HackerRank test, 4 questions. Same format as most experience posts here — except question 3 was SQL, and for the other questions you could choose Python or R. But I'm pretty sure most people here just use Python.

1. Date transformation

2. Arbitrary shopping (there was an image attached)

3. SQL question (pretty easy)

4. Given the center and radius of two circles, write a function to determine their positional relationship

My performance: I only fully got questions 3 and 4 right. Question 1 had some case I couldn't pass for no clear reason, and question 2 had a bunch of failing cases.

Result: a few days later I got a DS phone interview invite.

DS Phone Interview

Back-to-back, half an hour with one person.

They asked about my internship experience. I had done a decision tree, so they latched onto that: explain a decision tree, (they wanted to ask about random forest but I said I hadn't used it, so they skipped that), did you try other methods, why did you choose this method, if you had the chance would you use anything else, how do you know you're not overfitting, how do you pick tree depth.

They also asked how big my internship dataset was and how many features it had.

Then there was a probability question: you have one dollar, and you flip a fair coin. If it's heads, your money doubles; if it's tails, you walk away with whatever you have. For example, first flip heads → two dollars; another heads → four dollars; then tails → game over, you walk away with four dollars. How much would you be willing to pay to play this game. (I think that's roughly how the question went — it's an expected-value problem, and I've seen other people mention it here too.)