  A common situation in experimental physics is to have a signal which can not
be separated from a non-interfering background through the use of any cut. In
this paper, we describe a procedure for determining, on an event-by-event
basis, a quality factor (Q-factor) that a given event originated from the
signal distribution. This Q-factor can then be used as an event weight in
subsequent analysis procedures, allowing one to more directly access the true
spectrum of the signal.
