Normal probability plot of the mean radial velocity for single stars. The vertical dashed line marks the cluster mean velocity from Figure 4. The solid line is a linear best-fit to the data within the central 1.4 km s⁻¹ represented by vertical dotted lines. The inverse slope of this line is a measure of the observed cluster radial velocity dispersion, yielding 0.73 ± 0.09 km s⁻¹.