We consider non-constant coefficient elliptic equations of the type -div(a igtriangledown u) = f$, and employ the P-version of the finite element method as a numerical method for the approximate solutions. To compute the integrals in the variational form of the discrete problem we need the numerical quadrature rule scheme. In practice the integrations are seldom computed exactly. In this paper, we give an $L_2(Omega)$-error estimate of $Vert u = ilde{u}_p Vert_{0,omega}$ in comparison with $Vert u = ilde{u}_p Vert_{1,omega}$, under numerical quadrature rules which are used for calculating the integrations in each of the stiffness matrix and the load vector.