Epoch Capabilities Index switches to Bayesian model

The Epoch Capabilities Index is a system that measures AI model capability by converting benchmark test scores into comparable capability estimates using a statistical framework originally developed for educational testing. The organization behind it has switched from a frequentist statistical approach to a Bayesian approach to generate better-justified uncertainty estimates and enable direct comparisons of which models are likely more capable than others. The Bayesian model uses the same underlying logic as the previous method but provides improved estimates of uncertainty around capability measurements, while keeping capability scores for leading models largely unchanged.