[Fe/H] obtained with the Casagrande et al. (2008) method versus the spectroscopic metallicity. The blue dots with error bars represent the data points. The black line depicts a one-to-one relationship. The metallicity difference between the values of the calibrations and the spectroscopic measurements is shown below each [Fe/H]–[Fe/H] plot. The black dashed line is the zero point of the difference, and the red dotted line represents the average of the metallicity difference.