Worth Knowing

Updating the Epoch Capabilities Index methodology to use a Bayesian model

This methodological upgrade improves the statistical rigor of a prominent index used to aggregate benchmark scores and track the progress of frontier AI models.

Epoch AI has updated the methodology behind its Epoch Capabilities Index (ECI), transitioning from a frequentist approach to a Bayesian Item Response Theory model. This update replaces bootstrapping with Markov Chain Monte Carlo sampling and introduces a beta likelihood with benchmark-specific noise to provide more reliable uncertainty estimates and direct model comparisons.

  • Epoch AI
  • Claude 3.5 Sonnet
  • GPT-5

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