Correlation between the measurement uncertainty of the inner slope (from model B) with the number of GCs per galaxy (left panel) and the median error of the RV (right panel). The grey dashed line indicates the intrinsic scatter of the inner slope of 0.16, as determined by P17 and Auger et al. (2010). In order to constrain the intrinsic slope to the same level, the black solid line indicates the maximum measurement uncertainty needed when using ∼10 galaxies.