  The scalar strange-quark matrix element of the nucleon is computed with
lattice QCD. A mixed-action scheme is used with domain-wall valence fermions
computed on the staggered MILC sea-quark configurations. The matrix element is
determined by making use of the Feynman-Hellmann theorem which relates this
strange matrix element to the change in the nucleon mass with respect to the
strange-quark mass. The final result of this calculation is m_s < N | s-bar s|
N > = 49 +-10 +- 15 MeV and, correspondingly f_s = m_s < N | s-bar s |N > / m_N
= 0.051 +- 0.011 +- 0.016. Given the lack of a quantitative comparison of this
phenomenologically important quantity determined from various lattice QCD
calculations, we take the opportunity to present such an average. The resulting
conservative determination is f_s = 0.043 +- 0.011.
