Data Scientist Interview Questions

Showing 61–90 of 163 results

• Goldman SachsEasy·Data Scientist
  Count Palindromic Substrings

  This question tests your ability to identify palindromes within a string using expansion around centers or dynamic programming.

  Coding & AlgorithmsOnline AssessmentStringsTwo PointersDynamic Programming
• Goldman SachsEasy·Data Scientist
  Expected Number of Runs in Coin Tosses

  Tests understanding of linearity of expectation and indicator random variables through counting consecutive runs in a sequence of coin tosses.

  Statistics & MathOnline Assessmentprobabilityexpected-valuecombinatorics
• Goldman SachsEasy·Data Scientist
  Infer BA When AB Is the Identity

  This question tests the understanding of matrix invertibility, the properties of the identity matrix, and the fundamental differences between square and non-square matrix multiplication.

  Statistics & MathOnline AssessmentLinear AlgebraMatricesRank
• Goldman SachsEasy·Data Scientist
  Integrate a Two-Sided Exponential Density

  This question tests the ability to integrate probability density functions (PDFs) over specified intervals, specifically handling the absolute value function in symmetric distributions.

  Statistics & MathOnline AssessmentCalculusProbabilityDistributions
• GoogleEasy·Data Scientist
  Answer Google Behavioral Questions

  A set of four common Google Data Scientist behavioral interview questions covering self-introduction and fit, diagnosing and solving a team problem, communicating a missed deadline to stakeholders, and handling a team event with reluctant participants. The solution uses a STAR/STAR-L framework and explains the competencies Google scores for: collaboration, ownership, communication, judgment, and inclusion.

  Behavioral & LeadershipOnline Assessment
• GoogleEasy·Data Scientist
  Build next-word predictor with O(1) lookup

  This problem tests your ability to design a memory-efficient data structure for storing n-gram probabilities and performing fast lookups for the most likely next word.

  Coding & AlgorithmsOnline AssessmentHash MapData StructuresNLP
• HHBOHard·Data Scientist
  Define scalable train/validation for churn

  This question assesses the ability to design an end-to-end churn prediction pipeline, focusing on temporal integrity, handling class imbalance, and ensuring robust production deployment.

  Machine LearningOnline AssessmentChurnSystem DesignData Leakage
• HHBOHard·Data Scientist
  Design an A/B for rare cancellations

  This question evaluates a data scientist's competency in experimental design, rare-event power analysis, precise metric and guardrail definitions, variance-reduction covariate adjustment, sequential-testing decisions, monitoring/dashboard specification, and interpretation of heterogeneous treatment effects.

  Analytics & ExperimentationOnline Assessment
• HHeadlandsMedium·Data Scientist
  C++ Sliding-Window Mean of a Float Array With Inf, -Inf and NaN Handling

  Implement an O(n) sliding-window mean over a 32-bit float array containing IEEE-754 special values (+inf, -inf, NaN) without poisoning subsequent windows or suffering numerical drift.

  Software Engineering FundamentalsOnline Assessmentcppsliding-windowieee-754
• HHeadlandsMedium·Data Scientist
  What Cross-Validation Reduces: Bias, Variance, Type I or Type II Error

  This question tests your conceptual understanding of how k-fold cross-validation affects the generalization error and how the choice of 'k' influences the trade-off between bias and variance in model performance estimation.

  Machine LearningOnline AssessmentModel EvaluationCross-ValidationStatistics
• HHeadlandsMedium·Data Scientist
  t-Stat With an Added Orthogonal Regressor, Live Sharpe Check, and Absolute-Loss Estimator

  Solve three core quantitative problems covering OLS regression mechanics under orthogonal regressors, statistical significance of backtested Sharpe ratios in live deployment, and loss-function minimization for L1 error.

  Statistics & MathOnline AssessmentEconometricsSharpe RatioLinear Regression
• Hudson River TradingMedium·Data Scientist
  Count Smaller Numbers with Only Zero and One in Base Four

  Count the number of positive integers strictly less than n whose base-4 representation consists only of the digits 0 and 1.

  Coding & AlgorithmsOnline AssessmentMathBit ManipulationDigit DP
• 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
• Morgan StanleyMedium·Data Scientist
  Answer basic probability and statistics questions

  This problem tests your conceptual understanding of probability distributions, statistical bias in data collection, and the relationship between covariance and linear correlation.

  Machine LearningOnline AssessmentStatisticsProbabilityBias
• OneMain FinancialMedium·Data Scientist
  Determine Optimal Marketing Budget Allocation for Maximum Profit

  This interview question evaluates metric design, causal reasoning, experiment setup, diagnostics, SQL/statistical checks, and recommendations in a realistic interview setting. A strong answer for Determine Optimal Marketing Budget Allocation for Maximum Profit states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.

  Analytics & ExperimentationOnline Assessment
• OpenAIMedium·Data Scientist
  Analyze A/B Test Results for Subscription Conversion Rates

  Evaluates A/B test analysis for a limited-time free trial offer. Strong answers compute paid-conversion lift, account for trial starts and churn, test statistical significance, and make a launch decision using retained paid value, revenue, guardrails, and long-term holdouts.

  Analytics & ExperimentationOnline 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
• OpenAIMedium·Data Scientist
  Determine Metrics to Measure Free-Trial Impact on Subscriptions

  Determine Metrics to Measure Free-Trial Impact on Subscriptions evaluates metric design, causal reasoning, experiment setup, diagnostics, SQL/statistical checks, and recommendations in a realistic interview setting. A strong answer states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.

  Analytics & ExperimentationOnline Assessment
• OpenAIMedium·Data Scientist
  Identify Bugs in Python Script for User Assignment

  This question evaluates a candidate's ability to detect bugs and data-quality risks in a Python script, testing competencies in code review, reproducible randomization, idempotency, logging, duplicate-exposure safeguards, and safe experiment-assignment logic.

  Coding & AlgorithmsOnline Assessment
• OptiverEasy·Data Scientist
  Compute probabilities and expectations in random processes

  This question evaluates proficiency in probability theory, combinatorics, and mathematical expectation through a series of rapid-fire brain-teasers. It tests the ability to set up clean probabilistic models, apply the right technique, and derive exact closed-form answers under time pressure — skills commonly assessed in quantitative and data science interviews.

  Statistics & MathOnline Assessment
• OptiverHard·Data Scientist
  Find missing numbers in sequences

  This problem tests pattern recognition and algorithm design for identifying missing terms in a sequence that may follow arithmetic, geometric, polynomial, or linear recurrence rules.

  Coding & AlgorithmsOnline AssessmentAlgorithmsPattern RecognitionNumerical Analysis
• OptiverHard·Data Scientist
  Find next terms in sequences

  This question evaluates pattern recognition, numerical reasoning, and sequence-inference competency across arithmetic, fractional, and recurrence-style relationships, and falls under the Statistics & Math domain relevant for data scientist roles.

  Statistics & MathOnline Assessment
• OptiverHard·Data Scientist
  How to rank statements by likelihood

  This problem tests your ability to translate statistical distributions and categorical data into ranked probabilistic likelihoods, accounting for uncertainty and sample size variance.

  Machine LearningOnline AssessmentProbabilityStatisticsBayesian Inference
• OptiverMedium·Data Scientist
  Match alphanumeric patterns in a stream

  This question evaluates skills in exact and approximate alphanumeric string matching, streaming pattern lookup, noise-tolerant comparison, and performance-oriented data structures and encodings.

  Coding & AlgorithmsOnline Assessment
• OptiverMedium·Data Scientist
  Minimize moves to transform floor layouts

  This question evaluates algorithm design and combinatorial optimization skills, focusing on reasoning about minimal moves, greedy heuristics, and proving optimality within the Coding & Algorithms domain for data-science technical roles.

  Coding & AlgorithmsOnline Assessment
• OptiverHard·Data Scientist
  Solve probability and expectation problems

  This problem tests your ability to calculate expected stopping times in a discrete random walk and your understanding of conditional expectation and symmetry in probability.

  Statistics & MathOnline AssessmentProbabilityExpectationStochastic Processes
• 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
  Answer ancestor-walk queries on a rooted tree

  This question evaluates understanding of tree data structures and ancestor-walk queries, assessing competency in traversing rooted trees, interpreting parent arrays, and designing efficient query-processing methods for large n and q.

  Coding & AlgorithmsOnline 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