Distribution of perpendicular deviates. The fraction of stars in a given sample with deviates ≥D_⊥/σ is shown. In the presence of statistical variations only, the differential distribution of D_⊥/σ is a one‐sided Gaussian, indicated here by the dash‐dotted line. The presence of variability in excess of statistical deviations in a chosen sample will result in a larger fraction of the sample showing perpendicular deviates at much larger values of σ, as is the case for the Einstein‐RASSBSC (solid line), Einstein‐WGACAT (dotted line), and RASSBSC‐WGACAT (dashed line) samples; note that ~30%, 45%, and 35% of the stars in the respective samples show variability in excess of 5 σ.