Comparison of the mean relative radial velocity, v_∥(r), and the square root of its variance, σ_∥(r), measured from ΛCDM simulation halos using full 3D information (red lines), and LOS-velocity estimators only (black lines). Quantities are shown in bins of pair separation, r. Bootstrap errors (68% CL) are shown for the r = (1,5) h^-1 Mpc bins; we note that they are significantly larger than the differences between the black and red curves.