  For a number of reasons, the properties of integrated stellar populations are
distributed. Traditional synthesis models usually return the mean value of such
distribution, and a perfect fitting to observational data is sought for to
infer the age and metallicity of observed stellar populations. We show here
that, while this is correct on average, it is not in individual cases because
the mean may not be representative of actual values. We present a simple
mathematical formalism to derive the shape of the population's luminosity
distribution function (pLDF), and an abridged way to estimate it without
computing it explicitly. This abridged treatment can be used to establish
whether, for a specific case, the pLDF is Gaussian and the application of
Gaussian tools, such as the chi^2 test, is correct. More in general, our
formalism permits to compute weights to be attributed to different properties
(spectral features or band luminosities) in the fitting process. We emphasize
that our formalism does not supersede the results of traditionaly synthesis
models, but permits to reinterpret and extend them into more powerful tools.
The reader is referred to the original paper for further details.
