  We present magnetotransport studies performed on an extended set of (Ga,Mn)As
samples at 4.2 K with longitudinal conductivities sigma_{xx} ranging from the
low- to the high-conductivity regime. The anomalous Hall conductivity
sigma_{xy}^(AH) is extracted from the measured longitudinal and Hall
resistivities. A transition from sigma_{xy}^(AH)=20 Omega^{-1}cm^{-1} due to
the Berry phase effect in the high-conductivity regime to a scaling relation
sigma_{xy}^(AH) proportional to sigma_{xx}^{1.6} for low-conductivity samples
is observed. This scaling relation is consistent with a recently developed
unified theory of the anomalous Hall effect in the framework of the Keldysh
formalism. It turns out to be independent of crystallographic orientation,
growth conditions, Mn concentration, and strain, and can therefore be
considered universal for low-conductivity (Ga,Mn)As. The relation plays a
crucial role when deriving values of the hole concentration from
magnetotransport measurements in low-conductivity (Ga,Mn)As. In addition, the
hole diffusion constants for the high-conductivity samples are determined from
the measured longitudinal conductivities.
