Comparison between the PLZ coefficients obtained with the resampling in metallicity with those obtained using the entire data set. From top-left to bottom-right, the panels show the results for the α, β, γ, and δ coefficients, respectively. For each coefficient, different photometric bands are plotted using different symbols, as labelled in the top-left panel. In contrast, red-filled and white-filled symbols indicate the fit results including or excluding the δ parameter, respectively.