# Epoch AI updates its Capabilities Index to use Bayesian methodology

> Original title: We’ve updated the Epoch Capabilities Index (ECI) to use a Bayesian methodology. This improves uncertainty estimates and lets us compare m...

- Source: Epoch AI
- Published: 2026-11-04T21:31:03.000Z
- Bad Influence: https://badinfluence.news/items/zmtzs5gsfzaiysegzixpqz3sh
- Original: https://x.com/EpochAIResearch/status/2118093692246671634

## Summary

Epoch AI has updated its Epoch Capabilities Index (ECI) to use a Bayesian methodology, which improves uncertainty estimates and allows more accurate model comparisons even when individual ECI intervals overlap. Scores for frontier models are largely unchanged, with models stronger than GPT-4 moving less than 1 ECI point on average.

## Post

We’ve updated the Epoch Capabilities Index (ECI) to use a Bayesian methodology. This improves uncertainty estimates and lets us compare models more accurately, even when their individual ECI uncertainty intervals overlap.

Frontier model scores are largely unchanged: models stronger than GPT-4 move by less than 1 ECI point on average.

![Dot-and-whisker chart of the ECI and 90% interval for the 10 models that were state of the art when released, under the previous (frequentist) and new (Bayesian) methods. Each model's new estimate lies within its previous interval, from GPT-5 at 150 up to GPT-6 Astra near 169.](https://badinfluence.news/api/img-proxy?u=https%3A%2F%2Fpbs.twimg.com%2Fmedia%2FHWT6_PFaUAApXyA.png&mode=thumb&exp=1794096000&sig=6e41bb6c90f3ad95)