---
title: Diagnosing and Fixing Overfitting in Machine Learning with Python
url: https://www.dataloco.com/en/diagnosing-and-fixing-overfitting-in-machine-learning-with-python
published: 2026-09-13T09:10:13+00:00
language: en
section: Developers
source: https://machinelearningmastery.com/diagnosing-and-fixing-overfitting-in-machine-learning-with-python/
publisher: Dataloco
---

# Diagnosing and Fixing Overfitting in Machine Learning with Python

Overfitting has emerged as one of the most common challenges encountered when constructing machine learning models. It arises when a model learns the details and noise present in the training data excessively, rather than capturing the essential patterns that ensure better generalization to new, unseen data. Identifying whether a machine learning model is affected by this issue is vital for addressing it effectively and ensuring reliable performance in production settings.

The process begins with the creation of a synthetic dataset that is likely to lead to overfitting, followed by training a regression model on this data. The article outlines two primary methods for diagnosing overfitting, including visualizing the model alongside the training and test data.

A polynomial regression model was trained with a degree of 10, highlighting how higher-degree polynomials can tightly fit the training data, potentially leading to overfitting. The Mean Squared Error (MSE) for the training data was reported at 0.0052, while the test data showed a significantly higher MSE of 406.1920, indicating overfitting.

To remedy this situation, the article suggested simplifying the model by reducing the polynomial degree to 3. This adjustment resulted in a training MSE of 0.0139 and a test MSE of 0.0394, demonstrating improved generalization and a reduction in the severity of the error difference between training and test data.