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Prep plan
Updated weekly · Last refresh Aug 30

Pocket Gems Data Scientist Interview Questions

The questions to prepare for a Pocket Gems Data Scientist interview. Questions from real interview reports rank first. Updated weekly.

28questions
~4htotal time
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1
Machine LearningStart here. 4 questions · ~33 min
Supervised vs Unsupervised LearningEasy

Explain how supervised and unsupervised learning differ, and ground the distinction in a practical ML example.

Unsupervised LearningFeature EngineeringBias-Variance TradeoffPocket Gems
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2
A/B Testing & Experimentation4 questions · ~33 min
Plan Sample Size for In-App ExperimentMedium

Estimate sample size and power for an experiment, define MDE and guardrails, and decide whether the test is worth running.

MDEPower AnalysisSample SizePocket Gems
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3
Statistics & Probability3 questions · ~24 min
Testing a Conversion Rate DropMedium

Explain how to test whether an observed 5% conversion rate drop is statistically significant in an experiment or before-after comparison.

Hypothesis TestingData AnalysisStatistical SignificancePocket Gems
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4
Product Sense4 questions · ~33 min
Define Metrics for New FeaturesMedium

Define a success metric for a new feature that captures real user value, not just raw usage.

MetricsFeature Prioritizationuser valuePocket Gems
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5
Metrics4 questions · ~33 min
Diagnose Engagement Drop After ReleaseHard

Investigate whether a recent product release caused a sharp drop in Driver App engagement and identify where the decline is coming from.

DiagnosisTime SeriesEngagement MetricsPocket Gems
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6
Behavioral & Leadership3 questions · ~24 min
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7
More topics6 questions · ~49 min
Describe a Complex Transformation PipelineMedium

Explain a complex ETL transformation you built, including the main challenges and how you handled them.

ETLData ModelingQualityPocket Gems
Model Performance EvaluationEasy

Tests your ability to select metrics, validation strategy, and interpret results for ML models.

PrecisionAccuracyRecallPocket Gems
Pre vs Post Launch SQL AnalysisMedium

Tests SQL skills for event-based comparisons and feature launch impact analysis.

JoinsData WranglingCTEsPocket Gems
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Hands-on SQL practiceWrite and run real queries in the editor. 3 drills · ~30 min
7-Day Rider Retention in NYCHard
Practice
Practice drill

Compute 7-day NYC rider retention by signup cohort using joins, CTEs, date filters, and distinct retained-user aggregation.

Window FunctionsRetentionRunning TotalsUberAsana
SQL for MoM RetentionHard
Practice
Practice drill

Calculate cohort month-over-month retention for Thumbtack service professionals using CTEs, date truncation, joins, and aggregation.

Window FunctionsDate FunctionsRetentionThumbtack
Analyze Decision Impact by RegionEasy
Practice
Practice drill

Use joins, CASE WHEN, and date filtering to compare outcome rates before and after a decision.

Data WranglingDiagnosisAggregationsHarbourVest Partners
The finish line: interview-readyComplete all 28 questions plus 3 hands-on drills to finish this plan.