Using data mostly assembled by previous authors , we consider the linear correlation between the apparent radiative efficiency \epsilon _ { \gamma } ( defined as the ratio of isotropic equivalent radiative output to inferred isotropic equivalent kinetic energy of the blast ) and E _ { peak } ^ { \alpha } where 1.4 < \alpha < 2 , for 17 of 22 GRBs ( Lloyd-Ronning and Zhang , 2004 ) .
We note in a quantitative manner that this is consistent with the hypothesis that \epsilon _ { \gamma } and E _ { peak } are influenced by viewing angle .
We suggest a more general theoretically derived expression for this correlation that could be tested with a richer data set .
If the reduction in both \epsilon _ { \gamma } and E _ { peak } is due to viewing angle effects , then the actual radiative efficiency is \sim 7 .
We also find preliminary evidence ( with a small sample ) for a separate class of weak GRB afterglows .