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.
"I got asked a hardcore MCM DP question and I saw it on PracHub as well. Solved that question in 5 minutes. Without PracHub I doubt I could solve it in 5 hours. Though somehow didn't get hired, perhaps I guess I solved it too fast? /s"
"Believe me i'm a student here jn US. Recently interviewed for MSFT. They asked me exact question from PracHub. I saw it the night before and ignored it cause why waste time on random sites. I legit wanna go back and redo this whole thing if I had chance. Not saying will work for everyone but there is certainly some merit to that website. And i'm gonna use it in future prep from now on like lc tagged"
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"I was skeptical about the 'real questions' claim, so I put it to the test. I searched for the exact question I got grilled on at my last Meta onsite... and it was right there. Word for word."
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"Literally just signed a $600k offer. I only had 2 weeks to prep, so I focused entirely on the company-tagged lists here. If you're targeting L5+, don't overthink it."
"Coaches and bootcamp prep courses cost around $200-300 but PracHub Premium is actually less than a Netflix subscription. And it landed me a $178K offer."
"I honestly don't know how you guys gather so many real interview questions. It's almost scary. I walked into my Amazon loop and recognized 3 out of 4 problems from your database."
"Discovered PracHub 10 days before my interview. By day 5, I stopped being nervous. By interview day, I was actually excited to show what I knew."
"I recently cleared Uber interviews (strong hire in the design round) and all the questions were present in prachub."
"The search is what sold me. I typed in a really niche DP problem I got asked last year and it actually came up, full breakdown and everything. These guys are clearly updating it constantly."
Design fundraising experiment and guardrails
You plan to A/B test two online solicitation variants for the nonprofit's email campaign (subject line + suggested amount). Assume baseline conversion...
Assess 3.4M target and design experiments
Is a 3.4M-subscriber target reasonable under the case assumptions? Triangulate your answer via: a) a top-down TAM→SAM→SOM estimate; b) a bottom-up fun...
Design and critique teen-parent impact experiment
Causal Impact of Parental Registration on Teen Outcomes Meta plans to let parents register and link to their teen’s account. Leaders are concerned abo...
Evaluate and prioritize Facebook Groups
Analytics & Experimentation: Facebook Groups Context: You are evaluating how to measure and improve Facebook Groups. Assume access to standard product...
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...
Compute CIs, power, and multiple testing
A/B Testing Stats: Confidence Intervals, Power, Multiple Testing, and Clustering Context: You are planning an A/B experiment on a Bernoulli outcome (c...
Write SQL for cohort retention and ARPU
Using PostgreSQL, compute monthly signup cohort D30 retention and 30-day ARPU. Cohort month = date_trunc('month', signup_date). D30 retention = users ...
Select and tune XGBoost hyperparameters
Binary Classification Under Compute and Imbalance Constraints Context You are training an XGBoost model for a binary classification problem with: - 1,...
Write SQL for deliveries analytics
Write SQL for the following analytics tasks. Assume a PostgreSQL-like dialect unless otherwise stated. Treat "today" as 2025-09-01. Schema: - users(us...
Apply reinforcement learning to product decisions
Session‑level recommendations have stateful effects and feedback loops affecting long‑term retention. a) Formulate the problem as an MDP (state, actio...
Handle novelty and residual effects
Experiment design under novelty-decay and residual (carryover) effects Context You are testing a new UI that creates a novelty spike that decays over ...
Estimate variance for ratio metrics
KPI Variance via Delta Method and Inference Choices for ARPU Context You run experiments where each arm produces aggregate totals per analysis unit (e...
Design experiments under network interference
A/B Test Design for Search-Ranking in a Two-Sided Marketplace with Interference Context You need to evaluate a change to the search-ranking algorithm ...
Analyze promo anomaly and design risk guardrails
During a 2‑hour 11.11 flash sale (11:00–13:00), an account A123 places 80 orders in 10 minutes using 12 payment cards across 5 device_ids; 9 orders sh...
Design robust group size limiting for calls
Design the admission-control and enforcement algorithm to limit group-call size under real-world race conditions. Constraints: multiple SFU edges in m...
Drive stakeholder alignment under trade-offs
Decision Framework: Training Platform (Standard Vendor vs. Premium Vendor vs. Internal Build) Context You are responsible for driving a cross-function...
Quantify build-vs-buy training decision
Quantitative Decision Framework for Selecting a New Employee Training Program Context Your company must choose one of three ways to launch a new emplo...
Explain motivations, customer ownership, mentoring, and culture fit
1) Why are you leaving your current company? Answer in <90 seconds, avoid negativity, and tie your reason to specific growth you seek (e.g., owning an...
Add a conditional column in Python
Using pandas, add a derived column to a table based on multiple conditions with strict precedence and missing-value handling. Given the sample DataFra...
Explain handling pressure to bend rules
Describe a time you were explicitly asked to bend or break a rule for convenience (e.g., process, compliance, or data governance). How did you assess ...