  We present the results of our study of spectral energy distributions (SEDs)
of a sample of ten low- to intermediate-synchrotron-peaked blazars. We
investigate some of the physical parameters most likely responsible for the
observed short-term variations in blazars. To do so, we focus on the study of
changes in the SEDs of blazars corresponding to changes in their respective
optical fluxes. We model the observed spectra of blazars from radio to optical
frequencies using a synchrotron model that entails a log-parabolic distribution
of electron energies. A significant correlation among the two fitted spectral
parameters ($a$, $b$) of log-parabolic curves and a negative trend among the
peak frequency and spectral curvature parameter, $b$, emphasize that the SEDs
of blazars are fitted well by log-parabolic curves. On considering each model
parameter that could be responsible for changes in the observed SEDs of these
blazars, we find that changes in the jet Doppler factors are most important.
