en تحقیق در عملیات Operations Research پژوهشي Research This paper presents a new formulation for warehouse inventory management in a stochastic situation. The primary source of this formulation is derived from FP model, which has been proposed by Fletcher and Ponnambalam for reservoir management. The new proposed mathematical model is based on the first and the second moments of storage as a stochastic variable. Using this model, the expected value of storage, the variance of storage, and the optimal ordering policies are determined. Moreover, the probability of within containment, surplus, and shortage are computable without adding any new variables. To validate the optimization model, a Monte Carlo simulation is used. Furthermore, to evaluate the performance of the optimal FP policy, It is compared to (s*,S*) policy, as a very popular policy used in the literature, in terms of the expected total annual cost and the service level. It is also demonstrated that the FP policy has a superior performances than (s*,S*) policy. supply chain, warehouse inventory management, (s,S) policy, stationary and non-stationary demand, service level 277 284 http://ijiepr.iust.ac.ir/browse.php?a_code=A-10-540-1&slc_lang=en&sid=1 Masoud Mahootchi mmahootchi@gmail.com 180031947532846002060 180031947532846002060 No Amirkabir University of Technology Taher Ahmadi serkewtin@gmail.com 180031947532846002061 180031947532846002061 No Amirkabir University of Technology Kumaraswamy Ponnambalam ponnu@uwaterloo.ca 180031947532846002062 180031947532846002062 Yes University of Waterloo