Simpson's Paradox and Mutually Favorable Events
Colin R. Blyth · Journal of the American Statistical Association · 1973
This note points out that Simpson's Paradox [the possibility of P(A\B) P(A\B'C) and P(A\BC') > P(A\B' C')] is equivalent to the possibility of P(A\B) P(A\C) and P(A\BC') > P(A\C'). In the language of Kai-Lai Chung's “mutually favorable events” this is the possibility that B can be unfavorable to A even though B is conditionally favorable to A both given C and given C'.