Relations between T_eff and the (derived) metallicity [Fe/H] in FG stars of 47 Tuc (left panel, red points) and NGC 3201 (right panel, blue points) from M23 and M19, respectively. In each panel we list the Pearson's coefficient for the linear regression and the two-tail probability that the true correlation is zero. Circular black points indicate candidate binary stars (here and in the following figures). Error bars indicate typical errors taken from M19 and M23.