Monte Carlo test using a set of 1000 simulated light curves showing the input periods P_{cyc, in} and the returned periods P_{cyc, out}. The black lines show different P_{cyc, out}: P_{cyc, in} period ratios: the dotted line shows the 1:1 period ratio, and the upper and lower dashed line show the 2:1 and 1:2 period ratio, respectively. The cycle period uncertainties (shown as red error bars) were estimated from ten different sets of 1000 simulated light curves for each input period bin between 0.5–10 yr. The red crosses show the median value of P_{cyc, out} and the error bars show the median absolute difference between P_{cyc, in} and P_{cyc, out}. We omit error bars for P_{cyc, in} > 7 yr because the uncertainties become huge.