  The halo of the Miky Way might contain numerous and dense substructures
inside which the putative weakly interacting massive particles (suggested as
the main constituent of the astronomical dark matter) would produce a stronger
annihilation signal than in the smooth regions. The closer the nearest clump,
the larger the positron and antiproton cosmic ray fluxes at the Earth. But the
actual distribution of these substructures is not known. The predictions on the
antimatter yields at the Earth are therefore affected by a kind of cosmic
variance whose analysis is the subject of this contribution. The statistical
tools to achieve that goal are presented and Monte Carlo simulations are
compared to analytic results.
