Debug a model with overfitting

Last updated: September 13, 2025

Quick Overview

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

Plaid
Machine Learning
Data Scientist
Plaid
September 13, 2025
Data Scientist
Technical Screen
Machine Learning
Medium

2

7

443 solved


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

Machine learning questions at Plaid test both theoretical understanding and practical experience. This Technical 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
Regularization techniques (L1, L2, dropout)
Bias-variance trade-off
Model interpretability and explainability
Overfitting and underfitting
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
  • What regularization technique would you use and why?
  • What are the computational costs of this approach at scale?
  • How would you explain this model's predictions to a non-technical stakeholder?
  • How would you handle a highly imbalanced dataset?
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Explore ML Interview Prep
Sample Answer
Core Concept: Overfitting in Machine Learning

Overfitting occurs when a model learns the noise in the training data rather than the underlying distribution. This results in high accuracy on training data but poor generalization to unseen data, le...

How It Works: Mathematical Mechanisms

To combat overfitting, regularization techniques such as L1 (Lasso) and L2 (Ridge) regularization can be employed. L1 regularization adds a penalty equal to the absolute value of the magnitude of coef...


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