Average mass (left panels) and 1σ mass uncertainty (right panels) vs. residual of the RV rms after a correction based on the model in equation 1 for the different spectral types (one per panel) and masses: 1 M_Earth (red), 2 M_Earth (green), 3 M_Earth (brown), and 4 M_Earth (orange). In the right panels, the solid horizontal line indicates the 10% objective for PLATO, and the dashed line shows an indicative level of 20%. The dotted lines in the left panels indicate the ± 1 σ uncertainty envelope. For each row, the results are averaged over all configurations of habitable-zone periods and spot contrasts.