Global power spectrum histogram fitted with a χ² function. The upper subfigure is the histogram for the monthly binned light curve of S5 0716+714, at the scale corresponding to period ∼197 d, and the bottom subfigure is the histogram for the weekly binned light curve, at the scale corresponding to period ∼260 d. Five pre-trial confidence levels are shown in both graphs corresponding to 1 to 5σ significance in solid lines, whereas the post-trial confidence levels are shown in dashed lines.