  We present measurements of the clustering of galaxies as a function of their
stellar mass in the Baryon Oscillation Spectroscopic Survey. We compare the
clustering of samples using 12 different methods for estimating stellar mass,
isolating the method that has the smallest scatter at fixed halo mass. In this
test, the stellar mass estimate with the smallest errors yields the highest
amplitude of clustering at fixed number density. We find that the PCA stellar
masses of Chen etal (2012) clearly have the tightest correlation with halo
mass. The PCA masses use the full galaxy spectrum, differentiating them from
other estimates that only use optical photometric information. Using the PCA
masses, we measure the large-scale bias as a function of Mgal for galaxies with
logMgal>=11.4, correcting for incompleteness at the low-mass end of our
measurements. Using the abundance-matching ansatz to connect dark matter halo
mass to stellar mass, we construct theoretical models of b(Mgal) that match the
same stellar mass function but have different amounts of scatter in stellar
mass at fixed halo mass, sigma_logM. Using this approach, we find
sigma_logM=0.18^{+0.01}_{-0.02}. This value includes both intrinsic scatter as
well as random errors in the stellar masses. To partially remove the latter, we
use repeated spectra to estimate statistical errors on the stellar masses,
yielding an upper limit to the intrinsic scatter of 0.16 dex.
