Data Scientist Interview Questions
Practice 2,956 real Data Scientist interview questions for 2026. Data Scientist interview questions drawn from Meta, Capital One, Amazon, Google, TikTok and similar employers — real questions from actual interviews with detailed solutions — designed to accelerate your interview preparation for product analytics, ML and production data roles. This collection emphasizes the practical skills interviewers test: SQL and data manipulation, experiment design and A/B testing, statistical reasoning, Python coding for data problems, model evaluation and feature engineering, plus machine-learning system tradeoffs and metric design. What’s distinctive about modern data-science loops is the blend of product thinking and reproducible ML: expect hands-on SQL tasks and funnel analysis in screens, deeper experiment-design and causality questions in mid rounds, and coding or modeling challenges plus ML-system discussions in senior loops. Interviewers evaluate problem framing, statistical rigor, and how you communicate decisions to product partners. To prepare, prioritize daily SQL practice (CTEs, window functions), refresh hypothesis-testing and power calculations, rehearse concise metric-driven narratives, and build a few end-to-end model or experiment stories you can explain clearly under time pressure.
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Investigate marketplace metrics and experiment rollout
You are interviewing for a Senior Data Scientist role at a two-sided marketplace like Instacart, where customers place delivery orders and shoppers ch...
Compute Optimal Die Re-roll Strategy
A fair six-sided die pays its face value in dollars. You may roll up to three times total. - After the first or second roll, you may either keep the o...
Find probability of overlapping blooms
Overlap Probability of Two Random Bloom Periods Assumptions - Time is measured in days over a 30-day horizon. - Each flower begins blooming once, at a...
Solve relative-truth cat puzzle
Logic Puzzle: Directed Truth/Lie Rule and Cat Counts Three people (Asta, Bronya, Clara) each own a different number of cats (positive integers). When ...
Evaluate Marketplace Changes
You are a marketplace data scientist at a mobility and delivery platform. Discuss how you would evaluate the following product and algorithm changes: ...
Predict Future Car Sale Prices
You are given transaction-level data from car dealers for calendar year 2018, and you need to predict vehicle sale prices for transactions that will h...
How would you design an ETA prediction system?
Design an end-to-end ETA (Estimated Time of Arrival) system for a maps / ride-hailing / delivery product. Assume users request an ETA for a trip from ...
How to experiment on ETA reduction
Context You work on a consumer app where users see an ETA (estimated time to arrival/delivery) during a funnel (e.g., browsing → checkout → order plac...
Match readings with latest same-city humidity
Problem You are given two time-sorted lists of sensor readings: - Temperature records: (time, city, reading) - Humidity records: (time, city, reading)...
Diagnose and fix multicollinearity in income regression
You want to estimate the relationship between gender and income using a regression model, while controlling for other covariates such as: - age - educ...
Compute monthly break-even subscribers
Break-even Analysis for a Subscription Streaming Service Context A streaming startup incurs monthly fixed costs and per-subscriber variable costs and ...
Prove OLS invariance to linear transforms
You fit Model 1: y ~ X1 + X2. You also fit Model 2 using Z = [X1 − X2, X1 + X2] = X T where T = [[1,1], [−1,1]] (2×2, invertible). a) Prove that OLS p...
Narrow a confidence interval for a mean
You have a simple random sample with n = 100 and sample mean 100. The current 95% CI for the population mean is 100 ± 10, which a PM says is too wide....
Plan and analyze a ranking A/B test
Experiment Design: New Search Ranking Feature Context You are designing, running, and analyzing an online controlled experiment to evaluate a new sear...
Measure speaker impact without A/B testing
Your company launched an optional smart speaker on 2025-01-10. Adoption is voluntary; 6% of existing app users purchase within 60 days, and you cannot...
Choose a precise A/B test primary metric
A/B Test: Choose One Primary Metric for a Home-Screen CTA Color Change You are running an A/B test for an app that changes the color of its primary ho...
Compare two stores’ profits rigorously
Prompt: 14-Day Plan to Decide Which Snack Shop Will Be More Profitable Next Quarter Context: Two snack shops operate simultaneously at a school gate. ...
Verify subscriptions and analyze orders with SQL/Python
You are given two tables. Write SQL and Python (pandas) to answer the sub-questions precisely, handling edge cases, ties, and missing data. Schema - s...
Analyze Cancellation Change with Statistics
A/B change in cancellation rate (before vs after) Context: You are evaluating a small product tweak intended to reduce cancellations. Treat each trip ...
Fix failing tests and refactor code
You're given a small Python repo. After creating and activating a clean virtual environment, installing requirements, and running "pytest -q", two tes...