Comparison of observational precision of the frequencies of radial modes (l = 0) between our mode sets, some of the best Kepler observations (16 Cyg A and B, and KIC8006161), and a medium-quality Kepler observation. The blue data correspond to set 0 and the orange data to set 2. Set 1 is identical to set 2 with the exception that the four lowest radial-order modes were removed.