Probability density of black hole masses for the entire sample. We plot multiple realizations of our sample from the masses with uncertainties and their dependence on distance for the AGN sample. Thus, the distribution of the probability density of an individual black hole’s mass combines the statistical measurement uncertainties of both the mass and the distance. We do not include distance uncertainty in the XRB mass probability density because it generally does not affect it. The range of masses included in our sample is illustrated in this figure.