  The probability distribution function (PDF) of the ground-state energy in the
Sherrington-Kirkpatrick spin-glass model is numerically determined by
collecting a large statistical sample of ground states, computed using a
genetic algorithm. It is shown that the standard deviation of the ground-state
energy per spin scales with the number of spins, N, as N^{-\rho} with \rho
\simeq 0.765, but the value \rho=3/4 is also compatible with the data, while
the previously proposed value \rho=5/6 is ruled out. The PDF satisfies
finite-size scaling with a non-Gaussian asymptotic PDF, which can be fitted
remarkably well by the Gumbel distribution for the m-th smallest element in a
set of random variables, with m \simeq 6.
