# Bias Galaxy: Position, Presentation, Popularity, Exposure and IPS Correction

> Source: https://sukruyusufkaya.com/en/learn/oneri-sistemleri/bias-galaksisi-position-popularity-ips-correction
> Updated: 2026-05-13T13:29:34.005Z
> Category: Öneri Sistemleri
> Module: Module 2: Data, Labels and Ethics
**TLDR:** 5 important biases in recommender systems (position, presentation, popularity, exposure, selection), each with mathematical definition, ways to observe in log data, and Inverse Propensity Scoring (IPS) correction derivation + NumPy implementation.