A statistical approach to the study of AGN emission versus activity
  (with the detailed analysis of Mrk421)
  We discuss the theory and implementation of statistically rigorous fits to
synchrotron self Compton models for datasets obtained from multi-wavelength
observations of active galactic nuclei spectral energy distributions. The
methods and techniques that we present are, then, exemplified reporting on a
recent study of a nearby and well observed extragalactic source, Markarian 421.
