Conformal e-prediction

This paper discusses a counterpart of conformal prediction for e-values, conformal e-prediction . Conformal e-prediction is conceptually simpler and had been developed in the 1990s as a precursor of conformal prediction. When conformal prediction emerged as result of replacing e-values by p-values, it seemed to have important advantages over conformal e-prediction without obvious disadvantages. This paper re-examines relations between conformal prediction and conformal e-prediction systematically from a modern perspective. Conformal e-prediction has advantages of its own, such as the ease of designing conditional conformal e-predictors and the guaranteed validity of cross-conformal e-predictors (whereas for cross-conformal predictors validity is only an empirical fact and can be broken with excessive randomization). Even where conformal prediction has clear advantages, conformal e-prediction can often emulate those advantages, more or less successfully. • Re-examination of relations between conformal prediction and conformal e-prediction. • Design of conditional conformal e-predictors. • Guaranteed validity of cross-conformal e-predictors. • Design of criteria of predictive efficiency for conformal e-predictors. • Law of the iterated logarithm for e-prediction.