Diagnose Bias–Variance Trade-off in Supervised Learning
Overview
This question evaluates a data scientist's mastery of supervised learning diagnostics and modeling fundamentals, including the bias–variance trade-off, ordinary least squares assumptions, overfitting detection and mitigation, ensemble methods (boosting vs bagging), imbalanced classification metrics, missing data handling, and the prevalence of the normal distribution. Commonly asked in the Machine Learning and Data Science domain because these topics connect statistical theory with production-facing model evaluation and business impact in ranking systems, it assesses both conceptual understanding and practical application by requiring diagnostic reasoning and metric-driven trade-off analysis.
Supervised Learning Review (Customer-Facing Ranking Context)
You are designing and evaluating models for a customer-facing ranking service (e.g., ordering items by relevance). Answer concisely, referencing equations and business impact where helpful.
- Explain the bias–variance trade-off and how you diagnose it.
- List the key assumptions behind ordinary least squares (OLS) linear regression.
- How do you detect and mitigate overfitting?
- Compare boosting and bagging ensembles. When would you choose each?
- Which metrics would you choose for an imbalanced binary classifier and why?
- How would you handle missing data during training?
- Why is the normal distribution so common in statistical modeling?
Solution
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