  McFadden and Richter (1991) and later McFadden (2005) show that the Axiom of
Revealed Stochastic Preference characterizes rationalizability of choice
probabilities through random utility models on finite universal choice spaces.
This note proves the result in one short, elementary paragraph and extends it
to set valued choice. The latter requires a different axiom than is reported in
McFadden (2005).
