Relative errors calculated subject to various S/N values used in the sine waves injected into our ensemble of AGN light curves. Left: Relative errors obtained when S/N_sin was set to the value from PKS 2131–021 (heavy red lines) compared to when S/N_sin was set, at all frequencies, to 0, 1, 2, 3, or 5 (blue lines). Right: Relative errors obtained when AGN were cut from the sample based on their S/N_var at 95 GHz (green lines), compared to what was obtained when all AGN were used (red lines). The dashed green line shows the results when both an S/N_var < 5 cut was applied and S/N_sin was set to 3 at all frequencies.