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Citadel Securities Data Scientist Interview Questions

The questions to prepare for a Citadel Securities Data Scientist interview. Questions from real interview reports rank first. Updated daily.

35questions
~5htotal time
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1
Machine LearningStart here. 6 questions · ~49 min
Handle Highly Imbalanced ClassesMedium

Build a classifier for a highly imbalanced dataset and choose training and evaluation methods that surface rare positives.

Cross-ValidationFeature EngineeringSupervised LearningCitadel Securities
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2
Statistics & Probability7 questions · ~57 min
Statistical Significance for Strategy ComparisonEasy

Tests hypothesis testing intuition and ability to explain significance clearly for decision-making.

Hypothesis TestingStatistical SignificanceP-ValuesCitadel Securities
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3
Behavioral & Leadership14 questions · ~114 min
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4
More topics8 questions · ~65 min
Reconciling Discrepant Financial DataMedium

Explain how to reconcile discrepant financial datasets using joins, CTEs, aggregations, and exception classification.

JoinsData WranglingQualityCitadel Securities
Marketing Campaign A/B Test DesignMedium

Design a marketing campaign experiment with a pre-registered metric plan, power calculation, and ship rule that respects guardrails.

ExperimentationHypothesis TestingA/B TestingCitadel Securities
First Checks for Metric DropsEasy

Outline the first checks to diagnose a sudden drop in a core product metric, starting with data quality, scope, and decomposition.

Lagging IndicatorsLeading IndicatorsDiagnosisCitadel Securities
Design Product Metrics FrameworkMedium

Tests product measurement design and ability to define reliable leading and safety metrics.

North Star MetricGuardrail MetricsLeading IndicatorsCitadel Securities
Near-Real-Time Market Data PipelineHard

Tests pipeline architecture, data quality validation, and monitoring design for market data.

Data QualityStream ProcessingmonitoringCitadel Securities
Sparse Matrix Multiplication at ScaleHard

Tests systems-level performance reasoning for large-scale sparse linear algebra.

memory leakperformance baselinestechnical depthCitadel Securities
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Hands-on SQL practiceWrite and run real queries in the editor. 3 drills · ~30 min
Handling Missing DataEasy
Practice
Practice drill

Replace missing sales fields with defined defaults and return a consistently ordered dataset.

missing valuesdata cleaningnull handlingUniversity of MinnesotaThe Home DepotNationwide
Scenario-Based Business CaseHard
Practice
Practice drill

Aggregate project outcomes and present a defensible SQL-based business case analysis.

project experienceJoinsbusiness problemTikTok
Write SQL for a Specific ProblemMedium
Practice
Practice drill

Calculate each customer's completed 2025 order totals and classify customers by total value.

JoinsCTEsProblem SolvingEPAM Systems
The finish line: interview-readyComplete all 35 questions plus 3 hands-on drills to finish this plan.