# Class Imbalance Problem: 1:1,000,000 Fraud Ratios and Why Accuracy Lies

> Source: https://sukruyusufkaya.com/en/learn/anomali-tespiti/class-imbalance-problemi-accuracy-yalan
> Updated: 2026-05-13T13:04:49.092Z
> Category: Anomali Tespiti
> Module: Module 3: Data Preparation, Imbalanced Data and Labeling
**TLDR:** Fundamental challenge of anomaly detection: imbalanced class distribution. Why classical ML fails at 1:1,000,000 ratios, the accuracy paradox, mathematical and practical impacts of imbalanced learning, sectoral imbalance table.