Comparison of correlation methods for Sr and Zr. Left panel: PCCs and SCCs of Fe with Sr in stars with [Fe/H] < −2.5. Right panel: PCCs and SCCs of Fe with Zr in stars with [Fe/H] < −2.5. Y (not shown here) behaves in a similar way. Contrary to Fig. 3 (right panel) also stars with lower [Sr,Y,Zr/Fe] values than those with a weak r-process signature, such as HD 122563, are observed. HD 115444, CS22892−052, and CS31082−001 appear in the same order as seen in their increasing r-process strength.