Data Scientist Interview Questions
Practice 2,964 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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Navigate Cultural Differences in Cross-Functional Teams
Navigate Cultural Differences in Cross-Functional Teams Behavioral: Tell Me About Yourself + Handling Cultural Differences Context - Role: Data Scient...
Estimate Family Proportions and Explain Regression Anomalies
Estimate Family Proportions and Explain Regression Anomalies On-site Statistics Round Task Overview You are given a population of families that have e...
Diagnose a Sudden Revenue Decline: Analyses, Metrics, and Root-Cause Tests
Diagnose a Sudden Revenue Decline: Analyses, Metrics, and Root-Cause Tests Scenario A key revenue metric on Coinbase's dashboard suddenly declines—for...
Derive Probability of Even Sum in Bernoulli Trials
Derive Probability of Even Sum in Bernoulli Trials Probability Puzzles: Parity and Runs Context You are given two independent probability problems com...
Explain Google ADK and Compare with LangChain, AWS Bedrock
Explain Google ADK and Compare with LangChain, AWS Bedrock Scenario You are interviewing for a data scientist role in a technical phone screen. You pr...
Determine Length of Longest Unique Substring
Scenario Online assessment: coding portion that follows the SQL questions. Question Implement a function that, given a string s, returns the length of...
Compute an A/B test p-value by hand
In an A/B test on a game feature, you measure conversion rate (binary outcome). - Control: n₁ = 1000 users, x₁ = 120 conversions - Treatment: n₂ = 980...
Define metrics for new market expansion success
Define Metrics for New Market Expansion Success DoorDash is expanding into a new geographic market. Leadership asks what data the team should focus on...
Design and evaluate a new group call feature
Product / DS Case: Group Calls for Messenger Groups Messenger has Groups but does not currently support group calls. You are evaluating whether to bui...
Choose optimal posted price under adverse selection
You are negotiating to buy an item whose true quality is unknown to you. - With probability 0.7, the item is defective and would be worth $7,000 to yo...
Design an experiment to launch fractional shares
Context You work on a brokerage/investing app. The team is considering launching fractional share trading (users can buy/sell fractions of a stock/ETF...
Implement nth Fibonacci number
Implement nth Fibonacci number Problem Write a function that returns the n-th Fibonacci number. The Fibonacci sequence is defined as: - \(F(0)=0\) - \...
Compute invalid event percentage by pixel
Context You work on an ads pixel instrumentation platform. Each pixel emits events throughout the day; some events are missing (not observed) and some...
Design streaming stats with sliding window
Design streaming stats with sliding window Design a data structure that ingests an integer stream and supports online queries for maximum, mean, and m...
Calculate Pirated Usage and Revenue Loss
You are analyzing theme piracy on an e-commerce platform. Assume the analysis window is 2023-01-01 through 2023-12-31, all timestamps are stored in UT...
Compute multi-step Markov probabilities and estimate transitions
Problem (Markov Chain Probabilities) You are working with a discrete-time Markov chain over a finite set of states $S = \{s_1, \dots, s_n\}$. The chai...
Analyze Document Collaboration CSVs
Analyze Document Collaboration CSVs You are given two CSV files. document_activity.csv - page_id STRING — document identifier - user_id STRING — user ...
Implement Jackknife and Random Choice
Write Python code for two implementation tasks without using np.random.choice directly: 1. Jackknife-style resampling. Given a one-dimensional collect...
How would you evaluate emoji reactions launch?
You work on a Messenger-like chat app (not Meta). The product team plans to ship a new feature: Emoji Reactions (a user can long-press a message for 5...
Write SQL for rankings, state, and aggregations
You are given several independent datasets. For each dataset, write the required SQL query (ANSI SQL is fine). Assume dates are in UTC and DATE column...