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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"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."
Count Same-Day Registered Posters
You are given two tables: `text users - user_id: unique identifier for a user - registered_at: timestamp when the user registered posts - post_id: uni...
Assess Demand for Group Video Chat
Meta is considering adding a group video chat feature to an existing communication product that currently supports messaging and possibly 1:1 calling....
Should WhatsApp Launch Group Calls?
Assume WhatsApp currently supports only 1:1 audio and video calling and is considering launching group calling. You are the data scientist evaluating ...
Calculate Cohort Retention
You are given two tables: users - user_id BIGINT PRIMARY KEY - signup_ts TIMESTAMP user_events - user_id BIGINT - event_ts TIMESTAMP - event_name VARC...
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...
Compute early signals for user retention
You are given two tables that track signups and user transactions. Tables users - user_id (STRING, PK) — unique user - signup_ts (TIMESTAMP) — time th...
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...
Merge two sorted linked lists
Given two singly linked lists sorted in ascending order, merge them into one singly linked list that is also sorted in ascending order. Requirements: ...
Design Experiments Under Network Interference
You are a Senior Data Scientist for a gaming platform such as PlayStation. Answer the following experimentation questions. 1. A/A test validation: The...
How would you forecast bike demand?
You are given historical data from a shared city-bike system and asked to predict usage for a specific docking station during the next hour. Assume yo...
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...
Test whether US uploads more videos
You want to evaluate the hypothesis: > “US members upload more videos than non‑US members.” You have: Table: video_posts | column | type | |---|---| |...
How predict vehicles’ turn direction at intersection?
At an intersection, there are N vehicles stopped or moving slowly. For each vehicle you have historical time-series data up to the current time: - Pos...
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...
Write an average-income function
Given a Python list of dictionaries such as: records = [{"name": "a", "income": 100}, {"name": "b", "income": None}, {"name": "a", "income": 200}] Wri...
Determine Weekly Break-Even Point for Diaper Service
Diaper Service Unit Economics and Inventory Flow Scenario A weekly subscription diaper-delivery and cleaning service operates with these parameters: -...
Evaluate Dasher Initiatives with A/B Testing and Metrics
Scenario You are the product/analytics lead for a food-delivery marketplace. You must evaluate several Dasher-facing initiatives before deciding wheth...
Evaluate Account-Partner Onboarding with Success Metrics
Scenario DoorDash's account-partner team acquires new merchants onto the marketplace, and leadership wants to quantify how well that program works. Be...
Estimate impact without experiments and pick variant
Part A — Measuring impact when you cannot run an experiment You are a Staff Data Scientist working on a product change (feature/policy/model update). ...
Correct length-biased sampling from family-size survey
In a town, you visit a school and ask 100 kids: “How many children are in your family?” You observe: - 50 kids say their family has 1 child - 20 kids ...