Citadel–styleQuant ResearcherQuantitative ResearcherQuestion #31
If 75 customers are randomly assigned to three equal-sized databases, and all partitions are equally likely, what is the probability that two randomly selected customers, Bob and Ben, are in the same database?
Build Your Approach
State the assumptions, try a simple case, then work toward a general solution. Check the result and explain how it changes if an assumption changes.
Try the free diagnostic with worked solutions →Get Free Interview Prep Resources
More Citadel–Style Quant Researcher Questions
Explain the difference between Lasso and Ridge regression.Given three variables x, y, and z, where x is distributed as N(0,1), z is distributed as N(0, sigma^2), and y = x + z, with x independent of z: For a given observed value of y, what is the conditional distribution of x given y, i.e., p(x|y)?What is an O(n log n) sorting algorithm? Give an example and briefly explain how it works.Suppose you want to predict y and you have predictor vectors, each with known accuracy, variance, and sample length. How do you combine these predictors to minimize the residual standard error (RSE)?There are three random variables, X, Y, Z. The correlations between each pair of variables are the same, i.e., ρ = Corr(X,Y) = Corr(Y,Z) = Corr(Z,X). What is the tightest bound you can give for ρ? How about the general case for n random variables?
Practice the Reasoning Behind the Answer
Bring your target roles and interview timeline to a free quant consult. Discuss your preparation priorities and how Quant Blueprint’s lessons, practice and mock interviews can help.
Book a Free Quant ConsultYour goals · your preparation · your next steps