Simplified P_N (SP_N) equations are derived based on variational method using a modified version of ansatz originally proposed by Pomraning. New boundary and interface conditions are derived for the SP_N equations using the corresponding angular flux expression. The equivalence of equations, thus derived, along with its interface and boundary conditions with those of a specific case of Generalized SP_N (GSP_N), put forward by Chao, is brought out.