Estudio comparativo del impacto de la media y varianza del tiempo de entrega y de la demanda en el costo del inventario

Abstract

There are many perspectives about the impacts of the mean and standard deviation of both the demand and the lead-time over the inventory cost. Based upon statistical information, this study presents the results of two analyzed items: one with normal probability distribution and the other with uniform distribution for different values of the level of service, identifying which of the afore mentioned variables have greater influence on the cost. For the item with normal distribution, the variables with the greater impact were the standard deviation of the lead-time and, to a lesser extent, the average demand. For the article with uniform distribution, the four variables, i.e. the mean and standard deviation of both the demand and the lead-time were found to have an impact, with the average demand and the standard deviation of the lead time accounting for the greatest impacts, which also varied according to the level of service used. In all cases analyzed, the cost of inventory varied linearly with the standard deviation of lead time. The results are not affected by the structure of the inventory costs, including stock out and inventory maintenance, which are the two variables defining the level of service. In order to have an optimum inventory management it is recommended to select a provider offering reasonable lead-time with minimum variability.