Debug a model with data leakage

Last updated: December 6, 2025

Quick Overview

Your model shows poor recall. Walk through your debugging process and potential fixes.

Grubhub
Machine Learning
Data Scientist
Grubhub
December 6, 2025
Data Scientist
Phone Screen
Machine Learning
Medium

7

8

2,252 solved


Your model shows poor recall. Walk through your debugging process and potential fixes.

Machine learning questions at Grubhub test both theoretical understanding and practical experience. This Phone Screen question evaluates your knowledge of ML fundamentals and your ability to apply them to real-world problems.

What the Interviewer Expects
  • Explain the mathematical foundations with clarity
  • Discuss practical implementation considerations and hyperparameter tuning
  • Analyze the technique's strengths and weaknesses for different data types
  • Demonstrate understanding of evaluation methodology and metrics
  • Connect theory to real-world applications with concrete examples
Key Topics to Cover
Supervised vs unsupervised learning
Class imbalance handling
Model interpretability and explainability
Feature importance and selection
Gradient descent and optimization
How to Approach This
  1. Understand the bias-variance trade-off. High training accuracy but low test accuracy signals overfitting.
  2. Choose evaluation metrics carefully based on the problem. Accuracy alone is often insufficient.
  3. Feature engineering is often more impactful than model selection.
  4. Know when to use tree-based models (tabular data) vs neural networks (unstructured data).
  5. Handle class imbalance with SMOTE, class weights, or appropriate loss functions.
Possible Follow-up Questions
  • How would you detect and handle concept drift?
  • What are the computational costs of this approach at scale?
  • When would you prefer a simpler model over a complex one?
  • How would you explain this model's predictions to a non-technical stakeholder?
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Explore ML Interview Prep
Sample Answer
Core Concept: Data Leakage in Machine Learning

Data leakage occurs when the model inadvertently gains access to information from the training data that it should not have during the testing phase. This often leads to overly optimistic performance ...

How It Works: Identifying Data Leakage

Data leakage typically arises from improper splitting of datasets, where information from the test set leaks into the training set. For instance, if timestamped data is used, training on future data c...


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