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We estimate the radiative efficiency (epsilon) of individual type 1 SDSS QSOsby using their bolometric luminosities (L_{bol}) and accretion rates(\dot{M}_{\bullet,acc}), which may be related to the assembly histories andspins of the central massive black holes (MBHs). We estimate L_{bol} by usingthe empirical spectral energy distributions of QSOs and \dot{M}_{\bullet,acc}by fitting the observed optical luminosity(/-ies) with the thin accretion diskmodel, assuming the MBH masses given by the virial mass estimator(s)(M_{\bullet,vir}). We find an apparent correlation between epsilon andM_{\bullet,vir}, which is strong at redshift z \la 1.8, weak at z \ga 2, andconsistent with that found by Davis & Laor (2011) for 80 PG QSOs at z \leq 0.5.To investigate whether this correlation is intrinsic or not, we construct amock sample of QSOs according to the true MBH mass and Eddington ratiodistributions given in Kelly & Shen (2013). By comparing the results obtainedfrom the mock sample with that from the SDSS sample, we demonstrate that theapparent epsilon-M_{\bullet,vir} correlation can be produced by and mainly dueto the selection effects of the SDSS sample and the bias induced by the usageof M_{\bullet,vir} as the true MBH mass. The mean values of epsilon of thoseSDSS QSOs are consistent with being a constant \simeq 0.11-0.16 over theredshift range of 0.3 \la z \la 4. We conclude that the current SDSS QSO datais consistent with no strong intrinsic correlation between radiative efficiencyand true MBH mass and no significant redshift evolution of radiativeefficiencies.

Radiative Efficiency of Disk Accretion in Individual SDSS QSOs