  In quantum mechanics, the wavefunction predicts probabilities of possible
measurement outcomes, but not which individual outcome is realised in each run
of an experiment. This suggests that it describes an ensemble of states with
different values of a hidden variable. Here, we analyse this idea with
reference to currently known theorems and experiments. We argue that the
$\psi$-ontic/epistemic distinction fails to properly identify ensemble
interpretations and propose a more useful definition. We then show that all
local $\psi$-ensemble interpretations which reproduce quantum mechanics violate
Statistical Independence. Theories with this property are commonly referred to
as superdeterministic or retrocausal. Finally, we explain how this
interpretation helps make sense of some otherwise puzzling phenomena in quantum
mechanics, such as the delayed choice experiment, the Elitzur-Vaidman bomb
detector, and the Extended Wigner's Friends Scenario.
