  A simple model for medium modification of the jet function can be used to
extract the jet energy loss distribution through a parameterized form. We carry
out a comprehensive Bayesian analysis of the world data on single inclusive jet
spectra in heavy-ion collisions at both RHIC and LHC energies. We extract the
average jet energy loss $\langle \Delta E\rangle$ as a function of jet
transverse momentum $p_T$ for each collision system and centrality
independently. Assuming jet energy loss is proportional to the initial parton
density $\rho \sim dN_{\rm ch}/d\eta/\pi R_{\rm eff}^2$ as estimated from the
pseudorapidity density of charged hadron multiplicity $dN_{\rm ch}/d\eta$ and
the effective system size $R_{\rm eff}\sim N_{\rm part}^{1/3}$ given by the
number of participant nucleons $N_{\rm part}$, the scaled average jet energy
loss $\langle \Delta E\rangle/\rho \sim R_{\rm eff}^{0.59} p_T^{0.13}\ln p_T $
for jet cone-size $R=0.4$ is found to have a momentum dependence that is
slightly stronger than a logarithmic form while the system size or length
dependence is slower than a linear one. The fluctuation of jet energy loss is,
however, independent of the initial parton density or the system size.
