Data Scientist Statistics & Math Interview Questions
Practice the exact questions companies are asking right now.
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Compute probability an account is fake
A platform uses an automated classifier to flag potentially fake accounts. Assume: - Base rate: 2% of accounts are fake. - The classifier flags a fake...
Solve core probability and statistics questions
Answer the following short theory/computation questions (as in an OA multiple-choice section). Provide the key formula and a brief explanation. 1. Bay...
Solve Markov, OLS-rotation, and coin-toss probability
Answer the following three interview questions. 1) Basic properties of a Markov (transition) matrix Let \(P\) be a transition matrix of a (time-homoge...
Fake Accounts [AE]
Detecting and Managing Bad Accounts on a Social Platform 1) Probability of a Bad Account Sending Friend Requests Context: 1% of accounts are bad. Bad ...
Explain and interpret p-values correctly
Context You are evaluating a change to a fraud decision rule (e.g., a new threshold or step-up authentication rule). You run an experiment comparing C...
Model wins-until-failure and expected future wins
You are given a DataFrame df where each row summarizes a player’s performance until their first loss. Input df columns: - player_id (string/int) - win...
Compute probabilities and expectations in random processes
You are asked to solve the following probability/expectation questions. Unless stated otherwise, assume all random choices are uniform and independent...
Compute robust inference under skew and outliers
A/B test with skew, outliers, heteroskedasticity, missingness, and multiplicity You are comparing two independent product variants that produce a cont...
Compute decay, OLS, and classic probability results
You are asked several probability/statistics questions. 1) Radioactive decay (half-life) A radioactive atom has a half-life of 1 day. Assume each atom...
Solve probability and game-theory puzzles
You are interviewing for a quant trading internship. Answer the following probability / game-theory puzzles. 1) Two bottles, add/remove balls (100 rou...
Solve drunk-passenger probability and simulate outcome
Lost Boarding Pass Puzzle: Last Passenger's Seat Context: Technical screen for a Data Scientist (Statistics & Math). Setup - There are n passengers la...
Answer four core statistics questions
Problem set (timed) Answer the following four questions. 1) Covariance of order statistics Let \(X\) and \(Y\) be independent \(\mathrm{Unif}(0,1)\). ...
Choose tests under non‑normal, unequal variance
Heavy-Tailed, Heteroskedastic Metrics in A/B Tests (AOV example) Context: You are comparing two groups in an A/B test on a spend metric (e.g., Average...
Diagnose and interpret regression assumptions
OLS for Signups with Diagnostics and Alternatives You are given a cleaned dataset with the following columns: - signups: non-negative integer count ta...
Compute A/B sample size under clustering
A/B Test Sample Size With Unequal Allocation, Clustering, and Attrition Context You are planning a two-arm signup A/B test (binary outcome: convert vs...
Formulate hypotheses and compute AB test significance
A/B Test Snapshot: Pickup ETA Card Experiment You are analyzing a 7-day A/B test with equal allocation. Each request is an exposure; the primary outco...
Estimate population singletons from a 10% log
A daily search log has one row per query string. You draw a 10% simple random sample of rows without replacement. Define a “unique query” (singleton) ...
Solve estimation and probability brainteasers
Answer the following independent brainteaser questions. State any assumptions you need. 1) Tile a floor: A floor is 15 ft × 20 ft. You will cover it w...
Explain confounding with an Uber example
Question In the context of analyzing Uber/Uber Eats data, explain what a confounding effect is. 1. Define confounder and why it can bias an observed r...
Compute p-values, probabilities, and regularization choices
Answer all parts. A) Hand‑compute a two‑sided p‑value comparing two means using Welch’s t‑test. Sample A: n1=20, mean1=5.2, sd1=1.1. Sample B: n2=24, ...