  In determining the distances to stars within the Milky Way galaxy, one often
uses photometric or spectroscopic parallax. In these methods, the type of each
individual star is determined, and the absolute magnitude of that star type is
compared with the measured apparent magnitude to determine individual
distances. In this article, we define the term statistical photometric
parallax, in which statistical knowledge of the absolute magnitudes of stellar
populations is used to determine the underlying density distributions of those
stars. This technique has been used to determine the density distribution of
the Milky Way stellar halo and its component tidal streams, using very large
samples of stars from the Sloan Digital Sky Survey. Most recently, the
volunteer computing platform MilkyWay@home has been used to find the best fit
model parameters for the density of these halo stars.
