Left: black points indicate the median magnitude, m _med, vs. the median error, err_mag, in the ZTF data. Red and green points indicate the median magnitude vs. the light-curve standard deviation, σ with red outline indicating stars that do not meet a threshold of standard deviation, σ _mag, divided by median magnitude error, 2 × err_mag, larger than two, and green those that do. Right: excess variability, plotted as standard deviation (σ _mag) minus twice the median magnitude error (2 × err_mag) vs. inverse von Neumann statistic. Variable stars are selected as those having inverse von Neumann <1 and σ _mag > 2 × err_mag.