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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"10 years of experience but never worked at a top company. PracHub's senior-level questions helped me break into FAANG at 35. Age is just a number."
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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."
Decide event notification launch via experiments
Meta plans a new notification that tells you when friends are going to an event. Determine whether to launch it. 1) Design the experiment accounting f...
Choose clustering vs regression; explain KNN
When would you use clustering vs. regression on a business problem with partially labeled outcomes? Specify the decision criteria (label availability,...
Implement min, mean, median robustly
Implement three functions in Python without using numpy/pandas: (1) my_min(nums) returning the minimum in O(n) time and O(1) space; (2) my_mean(nums) ...
Run org-safe online experiment for recommender
Propose an online experimentation plan to evaluate the file recommender in production across multiple organizations where collaborators can influence ...
Define ride success metric for Uber
Define a single primary metric for "Uber ride success" Design one primary, comparable metric for ride success across markets and cohorts. Provide: 1) ...
Explain and validate A/B test assumptions
A/B Test Validity: Core Assumptions, Violations, Diagnostics, and Mitigations You are designing and evaluating an online A/B test for a large, multi-s...
Write SQL for active counts and YTD top driver
Given the following schema and sample data, write SQL to: (a) return the total count of active riders and active drivers on the platform; (b) return t...
Measure network effects and spillovers via experiments
Experiment design under network interference: direct and indirect effects Context You are evaluating a new social feature that can produce network spi...
Design and analyze end-to-end A/B test
A/B Test Design: Higher-Quality Friend Recommendations Context: You are updating the Friend Recommendation ("People You May Know") ranking to prioriti...
Diagnose and fix a flight-delay modeling setup
Flight Delay Modeling: Binary Target, Features, and Diagnostics You are modeling the probability that a flight arrives with a delay greater than 15 mi...
Aggregate radiology spend and derive fiscal month
Using Python/pandas, complete the tasks below. Assume the following CSV-like input, where service_dt is object dtype and amounts may be negative (adju...
Compute age-band spend and YoY in Georgia
Using ANSI SQL only, answer the three parts below on the following schema and samples. Assume dates are YYYY-MM-DD, paid_amt can be negative (adjustme...
Use regression vs cohorts for A/B estimation
Regression-adjusted estimation of treatment effects for contribution per order Context You are analyzing an A/B test at the order level. The outcome i...
Implement streaming SRM detector with late events
Implement a streaming detector for sample ratio mismatch (SRM) across many concurrent experiments. Input is two topic-partitioned streams: assignments...
Write SQL for 7-day geo-localized revenue dashboard
Write a single SQL query (assume PostgreSQL; tz_offset is an integer hour offset from UTC) to compute a 7-day dashboard by local user date for US vs A...
Design airport dispatch with ETA uncertainty
You control airport pickups with streaming ETAs for arriving flights and live driver locations/queues. Design an online dispatch algorithm that minimi...
Label new vs old users over time in SQL
Define users as “new” during the first 30 days inclusive after their signup_date, and “old” thereafter. Produce per-user, per-day labels over a window...
Quantify base-rate dilution in CTR
Weighted-Average CTR and Volume Requirements You are assessing the impact of introducing a new high-CTR event notification into an existing stream of ...
Decide under adverse signals and conflicts
Scenario: Pre-Launch Decision Under Mixed Signals You are preparing to launch a new messaging/notifications feature. Leading indicators are mixed: som...
Compute and rank top bad advertisers
SQL on ad safety. Assume the following schema and sample rows. Use ANSI SQL. Today is 2025-09-01; interpret “last 7 days” as 2025-08-26 00:00:00 to 20...