Completeness (top panels) and purity (bottom panels) of the optical/X-ray matches identified by applying our MHD identification method to the optical galaxies v195 volume-limited catalog of Tempel et al. (2014) and X-ray contours from RASS. Completeness and purity are presented as a function of bins of velocity dispersion of 100 km s⁻¹. The data was also split into three bins of redshift across the z range of the v195 catalog and the legend on panel (d) applies to all panels. Completeness and purity are shown for each bin of redshift and velocity dispersion. Left column: Completeness and purity for matches determined by an MHD calculated in megaparsecs, based on the redshift of the matching optical galaxy group. Our MHD method excels at identifying low-z groups even for σ below 300 km s⁻¹. Right column: Completeness and purity for matches determined by an MHD calculated in degrees. The completeness of matches is generally equal or lower when using degrees rather than physical units.