Radial velocity variability σRV of the observed stars vs. the luminosity/mass ratio. The solid line represents the scaling law proposed by Kjeldsen & Bedding (1995) to extrapolate solar type oscillations to other stars. To plot the scaling law a fixed value (1.2 M_⊙) for the mass has been assumed. To first approximation all M 67 evolved stars have the same mass. The continuous line is the scaling law, the dashed line is the best fit to the evolved stars data, which is perfectly consistent with the scaling law, when measurement uncertainties are taken into consideration.