  The possibility of radio galaxies being random sample of otherwise normal
elliptical galaxies is tested. Starting with the observed optical luminosity
functions for elliptical galaxies, it is shown that the probability of an
elliptical forming a radio source is a continuous, increasing function of
optical luminosity, precisely proportional to square of the optical luminosity
of the galaxy. Once the probability function is fixed, the luminosity function
of normal elliptical galaxies is used as input for Monte Carlo simulations that
reproduce the distribution of radio galaxies in the radio-optical luminosity
plane. Our results show that radio galaxies are luminosity biased, but
otherwise random sample of elliptical galaxies. This unified view of radio and
non-radio ellipticals also explains the well known difference of 0.5 mag in
average optical luminosity between FRI and FRII radio galaxies as a simple
selection effect. Specifically, FRII appear preferentially in smaller galaxies
because both radio and optical luminosity functions are steep, so there is a
negligible probability of observing a powerful radio source associated with a
bright galaxy; no intrinsic physical differences between FRI and FRII host
galaxies is required.
