  We discuss how different approaches to selecting member stars in kinematic
samples of dwarf spheroidal galaxies affect the estimates of their mass and
anisotropy of stellar orbits. We demonstrate that the selection of members is
an additional source of error compared to the usual uncertainties due to the
sampling of velocity moments. As an example we use the kinematic data set for
202 stars in the Fornax dwarf galaxy for which we model the velocity dispersion
profile and estimate the mass-to-light ratio and anisotropy assuming that mass
follows light. We also show that stronger constraints on these parameters can
be obtained if kurtosis of the velocity distribution is included in the
analysis. Using the Besancon model of the Milky Way we demonstrate that the
majority of contamination in Fornax probably comes from the Milky Way stars.
