Applied Statistics & Machine Learning
This area measures your ability to select, train, and evaluate models that solve real business problems. Expect to justify modeling choices, articulate assumptions, and choose metrics aligned with objectives (classification vs. regression, ranking vs. forecasting). You will likely be asked to compare approaches and reason about trade-offs under constraints.
Be ready to go over:
- Core statistics: distributions, hypothesis testing, confidence intervals, p-values vs. practical significance
- Model selection & validation: cross-validation, regularization, bias-variance, hyperparameter tuning
- Metrics & diagnostics: ROC-AUC, PR-AUC, F1, RMSE/MAE, lift, calibration, residual analysis
- Advanced concepts (less common): time-series cross-validation, survival analysis, SHAP/feature importance caveats, causal inference basics
Example questions or scenarios:
- "You have imbalanced classes—how do you choose and justify your metric and model?"
- "Walk me through how you would validate a forecasting model for weekly demand."
- "Your XGBoost model outperforms logistic regression on AUC but underperforms on PR-AUC. What do you do and why?"
Coding & Data Manipulation (Python + SQL)
We test your ability to write clean, efficient code to explore data, engineer features, and answer questions. Interviews often blend Python data wrangling and SQL querying to ensure you can build analyses end-to-end.
Be ready to go over:
- Python data stack: pandas/numpy operations, groupby/merge/reshape, handling missing/outliers
- SQL fluency: joins, window functions, aggregations, subqueries, CTEs, performance considerations
- Code quality: readability, modularity, testing simple helpers, reproducibility
- Advanced concepts (less common): vectorization trade-offs, basic complexity, query optimization basics
Example questions or scenarios:
- "Given two tables (transactions, customers), compute 30-day rolling revenue per customer using SQL."
- "In pandas, convert event logs to session-level features; discuss edge cases."
- "Refactor a messy notebook into functions and explain testing strategy."
Experimentation & Causal Reasoning
Many projects require A/B testing or evidence of causal impact. We assess how you design experiments, pick metrics, and interpret results responsibly.
Be ready to go over:
- Test design: randomization, power, sample size, guardrail metrics
- Analysis: difference-in-means, non-parametrics, multiple testing, pitfalls (peeking)
- Alternatives: quasi-experiments when RCTs are infeasible
- Advanced concepts (less common): CUPED, inverse propensity weighting, diff-in-diff assumptions
Example questions or scenarios:
- "Design an A/B test to improve signup conversion; define primary/secondary metrics."
- "Results are not statistically significant but business sees a lift—how do you respond?"
- "Randomization failed post-hoc. How do you analyze and communicate risk?"
Data Wrangling, Pipelines, and Visualization
Strong Data Scientists create reliable pipelines and clear visuals that drive decisions. We evaluate how you clean data, automate steps, and present insights succinctly.
Be ready to go over:
- Data quality: missing data strategies, deduplication, anomaly detection
- Pipelines: reproducibility, version control, environments, scheduling basics
- Visualization & storytelling: chart selection, avoiding misrepresentation, dashboard fundamentals
- Advanced concepts (less common): data contracts, data validation tests (e.g., Great Expectations)
Example questions or scenarios:
- "Build a minimal, reproducible pipeline for a weekly churn score refresh."
- "Which visualization best explains a precision-recall trade-off to non-technical leaders?"
- "You inherit a flaky CSV-based pipeline—what’s your stabilization plan?"
Business Acumen & Communication
We measure how well you translate data into decisions. You must connect analyses to strategy, articulate risks, and influence stakeholders.
Be ready to go over:
- Problem framing: turning an ambiguous prompt into testable hypotheses
- Prioritization: scoping MVPs, choosing high-ROI features, communicating trade-offs
- Stakeholder alignment: tailoring depth/format to the audience
- Advanced concepts (less common): north-star metrics, cost-sensitive modeling, scenario planning
Example questions or scenarios:
- "A stakeholder wants a complex deep model—how do you challenge and reframe to meet the actual goal?"
- "Tell a story of a project that changed course based on your analysis."
- "Explain your model to an executive in 90 seconds—what do you include and exclude?"