The result of poluting a mock planet-host sample with comparison stars following the procedure described in Sect. 5.2. Upper panel: dependence of the average offset and associated dispersion on the number N of planet-host stars in the mock planet-host star population of 30 stars. Lower panel: z-score of the offset as calculated relative to zero as a function of the same parameter N. The dashed line is a visual aid, representing an offset of zero on the upper panel and a z-score of zero in the lower one.