Nonparametric discriminant analysis for antisymmetric averages of the north–south travel-time differences, , in filter TD3 (top), and for the vertical vorticity, , in filter TD4 (bottom), for a subset of regions with matched distributions of average magnetic flux in the same format as Figure 1. The results are qualitatively very similar to those seen in Figures 5 (bottom) and  6 for the full samples. The largest change is an increase in the uncertainties caused by the smaller sample sizes.