Upper panel: average s-process abundance ratios with respect to Fe, plotted as functions of [Fe/H]. Bottom panel: average s-process abundance ratios with respect to Eu, plotted as functions of [La/Eu]. See the text for how the averages were computed. In each panel, the solid lines represent the means for each group, and the dotted lines represent the sample deviations σ. Symbols are as in Fig. 6.