Time series R_var(t) of the quarterly measured variability ranges of four Kepler stars. The time series in panels a)–c) pass our selection criterion that randomly permuting the time series R_var of this star yields a higher peak in the Lomb-Scargle periodogram in less than 5% of all tested cases (FAP < 5%), whereas panel d) shows a time series with (FAP > 5%). The red curve shows the best sine fit to the data, and the dashed black line indicates the mean variability of the star. The R_var(t) time series shown in panels a)–d) exhibit false alarm probabilities FAP = 1.0%, FAP = 0.5%, FAP = 0.3%, and FAP = 17.9%, respectively.