Distributions of low-metallicity candidates with 12 + log O/H ≤ 7.65 (N = 287, the same objects as those shown in Fig. 2a by magenta symbols) on a) the redshift z; b) the extinction-corrected absolute SDSS g-magnitude M_g; c) the extinction coefficient C(Hβ); d) the equivalent width EW(Hβ) of the Hβ emission line; e) the total stellar mass M_⋆; f) the mass M_y of the young stellar population. Dotted vertical lines in all panels indicate mean values of the distributions.