effect algebra; modular atomic effect algebra; subadditive state; MacNeille completion of an effect algebra
Lattice effect algebras generalize orthomodular lattices and $MV$-algebras. We describe all complete modular atomic effect algebras. This allows us to prove the existence of ordercontinuous subadditive states (probabilities) on them. For the separable noncomplete ones we show that the existence of a faithful probability is equivalent to the condition that their MacNeille complete modular effect algebra.