  We explore the relationship between two figures of merit for an adiabatic
quantum computation process: the success probability $P$ and the minimum gap
$\Delta_{min}$ between the ground and first excited states, investigating to
what extent the success probability for an ensemble of problem Hamiltonians can
be fitted by a function of $\Delta_{min}$ and the computation time $T$. We
study a generic adiabatic algorithm and show that a rich structure exists in
the distribution of $P$ and $\Delta_{min}$. In the case of two qubits, $P$ is
to a good approximation a function of $\Delta_{min}$, of the stage in the
evolution at which the minimum occurs and of $T$. This structure persists in
examples of larger systems.
