α factor versus photometric precision for sample A (left panel) and sample B (right panel) for Kepler observations. Those records for single long observation of isolated stars observed in an uncrowded pixel, i.e. light curves of resolved targets without contamination of additional sources. Extreme-case limits for spot- and faculae-dominated stars are shown as horizontal dashed linesin red and green, respectively. The individual data points are coloured according to the detected variability range for that particular star. This is consistent with the preceding figure, Fig. 4. The error bars represent 2-σ uncertainties of the α values distribution over all Kepler quarters available per star. Gray rhomboids represent data points that lie more than 2-σ from the centre of the distribution.