ν_c, z − L_iso relation obtained from the synchrotron GRBs in the multi-bin sample. We show multiple time bins from different GRBs with circles of the same colors. The number inside the circles represents the bin number that data point is associated with. The straight black line represents the best-fit line from the linear fit, while the dashed-line the best-fit line obtained from the ν_c, z − L_iso relation in the single-bin sample. The green-shaded area shows the 3σ scatter region of the relation.