Data Scientist Interview Questions

Showing 1–26 of 26 results

• AmazonMedium·Data Scientist
  Diagnose MySQL joins and GROUP BY/HAVING errors

  This question evaluates mastery of SQL join semantics (LEFT, RIGHT, FULL OUTER emulation, CROSS), NULL equality and duplicate handling, GROUP BY/HAVING behavior under ONLY_FULL_GROUP_BY, aggregation result shaping and type/format conversions in the Data Manipulation (SQL/Python) domain.

  Data Manipulation (SQL/Python)Online Assessment
• Boston Consulting GroupMedium·Data Scientist
  Merge and Clean Customer Order Data for Analysis

  This question evaluates proficiency in data manipulation with pandas and SQL concepts, focusing on dataset merging, missing-value handling, and computing derived aggregate columns such as total_spent.

  Data Manipulation (SQL/Python)Online Assessment
• Boston Consulting GroupMedium·Data Scientist
  Merge and Concatenate Inconsistent Order Files with Pandas

  This question evaluates proficiency with pandas-based data manipulation, including schema alignment, column renaming, type casting, and vertical concatenation when merging CSV files.

  Data Manipulation (SQL/Python)Online Assessment
• CVS HealthMedium·Data Scientist
  Create Views, Insert, and Update Correctly

  This question evaluates SQL data-manipulation competencies including view creation, aggregate joins, INSERT/UPDATE operations, and reasoning about temporal effects on computed aggregates such as historical customer spend.

  Data Manipulation (SQL/Python)Online Assessment
• CVS HealthMedium·Data Scientist
  Create and query an e-commerce schema

  This question evaluates SQL schema design and data manipulation competencies, including defining PostgreSQL table types and constraints, inserting exact datasets, composing aggregate and join queries with date-based filters, and performing DML updates with verification.

  Data Manipulation (SQL/Python)Online Assessment
• Capital OneMedium·Data Scientist
  Aggregate exam scores with NULL handling

  This question evaluates proficiency in SQL data manipulation, specifically joins (including LEFT JOIN behavior), NULL handling with ISNULL/COALESCE, conditional aggregation, distinct counts, and date-based filtering within the Data Manipulation (SQL/Python) domain, focusing on practical application of query-writing skills.

  Data Manipulation (SQL/Python)Online Assessment
• Capital OneMedium·Data Scientist
  Find top category per region in Aug 2025

  This question evaluates proficiency in SQL data manipulation skills such as joining related tables, aggregating revenue, filtering by date and status, and implementing deterministic tie-breaking for categories.

  Data Manipulation (SQL/Python)Online Assessment
• Capital OneMedium·Data Scientist
  Fix dash dates and aggregate watch time

  This question evaluates data-cleaning and aggregation competencies, focusing on handling nonstandard missing-date markers, forward-filling in spreadsheets, correct date-range filtering, pivot-table summarization, and concise pandas grouping and aggregation.

  Data Manipulation (SQL/Python)Online Assessment
• Capital OneMedium·Data Scientist
  Merge CSVs and build revenue pivot with pandas

  This question evaluates proficiency in data manipulation and ETL using pandas, covering robust file I/O, join/merge semantics, null/coalescing behavior, date parsing, aggregation, and pivoting.

  Data Manipulation (SQL/Python)Online Assessment
• Capital OneMedium·Data Scientist
  Merge ad CSVs and compute CTR

  This question evaluates SQL data manipulation competencies such as cleaning and merging CSVs, forward-filling missing dates, correct multi-table joins without duplication, use of window functions, time-windowed aggregations, and computation of click-through rate (CTR).

  Data Manipulation (SQL/Python)Online Assessment
• IBMEasy·Data Scientist
  Write SQL to compute max and min marks

  This question evaluates a candidate's ability to perform basic data aggregation in SQL, specifically computing summary statistics from a single table. It is commonly asked to assess competence in data manipulation and query result shaping within the Data Manipulation (SQL/Python) domain, focusing on practical application of SQL aggregation rather than purely conceptual theory.

  Data Manipulation (SQL/Python)Online Assessment
• OpenAIMedium·Data Scientist
  Design Schema and Logic for Subscription Event Tracking

  This question evaluates proficiency in event-driven data modeling, temporal state derivation, and implementation of SQL/Python logic to compute per-user subscription status and history within the Data Manipulation (SQL/Python) domain.

  Data Manipulation (SQL/Python)Online Assessment
• OpenAIMedium·Data Scientist
  Design Schema for Accurate Subscription State Tracking

  This question evaluates proficiency in temporal schema design and event-level data modeling, focusing on reconstructing time-varying subscription state using SQL and Python in the Data Manipulation (SQL/Python) domain.

  Data Manipulation (SQL/Python)Online Assessment
• OOtherMedium·Data Scientist
  Write SQL to analyze response accuracy and speed

  This question evaluates proficiency with SQL-based data manipulation and analytical querying on relational assessment data, including aggregation, grouping, joins, windowed ranking, and use of PostgreSQL statistical functions to analyze accuracy and response-time metrics.

  Data Manipulation (SQL/Python)Online Assessment
• OOthersEasy·Data Scientist
  Compute per-coin quarterly amounts and totals

  This question evaluates competence in SQL data manipulation—specifically time-based conditional aggregation, grouping, joins, and handling entities with no activity—to compute per-coin quarterly sums and year-to-date totals.

  Data Manipulation (SQL/Python)Online Assessment
• Point72Hard·Data Scientist
  Build the auction status table

  This problem tests advanced SQL skills, specifically the ability to perform window functions, handle state transitions, and aggregate time-series data to reconstruct the final status of entities.

  Data Manipulation (SQL/Python)Online AssessmentSQLWindow FunctionsData Aggregation
• StripeMedium·Data Scientist
  Write SQL to detect recurring non-subscription users

  This question evaluates a candidate's ability to perform advanced SQL data manipulation and temporal pattern detection in transactional datasets, including attribute-based matching (amount and card fingerprint) and filtering by transaction status.

  Data Manipulation (SQL/Python)Online Assessment
• TikTokMedium·Data Scientist
  Count buggy vs non-buggy by employer

  This question evaluates proficiency in SQL data manipulation—particularly conditional aggregation and join semantics—for counting categorized records across related tables in a data science context.

  Data Manipulation (SQL/Python)Online Assessment
• TikTokMedium·Data Scientist
  Select max-discount product per category

  This question evaluates proficiency in data manipulation and SQL querying—specifically use of window functions versus set-based alternatives, group-level ranking and tie-breaking, NULL-aware expressions, and numeric precision when computing discounts within the Data Manipulation (SQL/Python) domain.

  Data Manipulation (SQL/Python)Online Assessment
• Two SigmaMedium·Data Scientist
  Analyze NYC taxi trips efficiently over last 7 days

  This question evaluates proficiency in time-series filtering, relational joins, grouped aggregations (median and high-percentile calculations), numeric stability of percentile methods, and performance-aware vectorized data manipulation using SQL or pandas.

  Data Manipulation (SQL/Python)Online Assessment
• WayfairEasy·Data Scientist
  Clean scores and return top 5 students

  This problem tests your ability to clean tabular data by performing conditional imputation and applying window functions to rank performance metrics.

  Data Manipulation (SQL/Python)Online AssessmentPandasData CleaningImputation
• WayfairEasy·Data Scientist
  Find top buyer in earliest 10-year window

  This question tests the ability to filter data by date ranges, group transactional records by user, and use window functions or aggregations to identify a specific record based on criteria.

  Data Manipulation (SQL/Python)Online AssessmentSQLAggregationWindow Functions
• WayfairEasy·Data Scientist
  Solve SQL and Python OA tasks

  This question evaluates SQL and pandas data-manipulation skills, including joined aggregations over date windows, handling of missing values with median imputation, and multi-criteria sorting and tie-breaking.

  Data Manipulation (SQL/Python)Online Assessment
• WaymoMedium·Data Scientist
  Analyze User Ride Activity with SQL

  Solve four SQL analytics tasks on ride and user tables: inactive users, monthly rides and ratings, low-frequency users by city, and first-versus-third active-month ratings. The walkthrough emphasizes outer joins, date boundaries, aggregation grain, window functions, and weighted averages.

  Data Manipulation (SQL/Python)Online Assessment
• WaymoMedium·Data Scientist
  Compute Ride Metrics in SQL

  This question evaluates SQL data manipulation skills, covering joins between normalized tables, timezone-aware date filtering and calendar-month grouping, aggregation and NULL-aware averages, counting distinct and inactive users, and cohort/retention analysis.

  Data Manipulation (SQL/Python)Online Assessment
• WaymoMedium·Data Scientist
  Implement a Safe Average Function in Python

  Implement a Python average function that returns zero for an empty list and explain its time and space complexity. Clarify numeric types, missing values, NaN behavior, streaming alternatives, precision concerns, and the tests needed for a reliable data utility.

  Data Manipulation (SQL/Python)Online Assessment