  We have tested a relative spectral lag (RSL) method suggested earlier as a
luminosity/redshift (or distance) estimator, using the generalized method by
Schaefer & Collazzi. We find the derivations from the luminosity/redshift-RSL
(L/R-RSL) relation are comparable with the corresponding observations. Applying
the luminosity-RSL relation to two different GRB samples, we find that there
exist no violators from the generalized test, namely the Nakar & Piran test and
Li test. We also find that about 36 per cent of Schaefer's sample are outliers
for the L/R-RSL relation within 1$\sigma$ confidence level, but no violators at
3$\sigma$ level within the current precision of L/R-RSL relation. An analysis
of several potential outliers for other luminosity relations shows they can
match the L/R-RSL relation well within an acceptable uncertainty. All the
coincident results seem to suggest that this relation could be a potential tool
for cosmological study.
