# Epoch AI updates its Capabilities Index to use a Bayesian model

> Original title: Updating the Epoch Capabilities Index methodology to use a Bayesian model

- Source: Epoch AI
- Published: 2026-11-04T00:00:00.000Z
- Bad Influence: https://badinfluence.news/items/bz1z71o70sduomapk7h521xat
- Original: https://epoch.ai/publications/eci-bayesian-methodology

## Summary

Epoch AI says it has updated the Epoch Capabilities Index (ECI), which tracks AI model capability using benchmark results, to a Bayesian methodology. The change is meant to provide better-justified uncertainty estimates and to calculate how likely one model is to be more capable than another. The ECI is based on Item Response Theory, and the previous version used a frequentist fit with bootstrapped confidence intervals.