Journal Name:
- Journal of Industrial Engineering and Management
Abstract (2. Language):
Purpose: One of the most usual indicators to measure the performance of any
inventory policy is the mean stock level. In the generalized base stock, periodic
review policy, the expected mean stock during the replenishment cycle is usually
estimated by practitioners and researchers with the traditional Hadley-Whitin
approximation. However it is not accurate enough and exact methods suggested on
the related literature focus on specific demand distributions. This paper proposes a
generalized method to compute the exact value of the expected mean stock to be
used when demand is modelled by any uncorrelated, discrete and stationary
demand pattern.
Design/methodology/approach: The suggested method is based on computing
the probability of every stock level at every point of the replenishment cycle for
which it is required to know the probability of any stock level at the beginning of
the cycle and the probability transition matrix between two consecutive periods of
time. Furthermore, the traditional Hadley-Whitin approximation is compared with
the proposed exact method over different discrete demand distributions
Findings: This paper points out the lack of accuracy that the Hadley-Whitin
approximation shows over a wide range of service levels and discrete demand
distributions.
Research limitations/implications: The suggested method requires the
availability of appropriate tools as well as a sound mathematical background. For
this reason, approximations to it are the logical further research of this work.
Practical implications: The use of the Hadley-Whitin approximation instead of
an exact method can lead to underestimate systematically the expected mean stock
level. This fact may increase total costs of the inventory system.
Originality/value: The original derivation of an exact method to compute the
expected mean stock level for the base stock, periodic review policy when demand
is modelled by any discrete function and backlog is not allowed.
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FULL TEXT (PDF):
- 2
194-205