什么是service level，如何由此计算safety factor？

icetea_cn

附件是MIT有关Inventory management课程中有关safety stock的部分。

xuyongshuo

原帖由 icetea_cn 于 2008-7-22 10:05 发表
1.        Types of service level
For inventory models we often refer to two types of service level:
Type I - The service level is defined as the probability of stocking out when there is an order event in the lead time. (Equivalently we can define it as the probability of not stocking out when there is an order event in the lead time).

Type II - The service level is defined as the percentage of demand that is not met from inventory, or equivalently, the percentage of demand that is met from inventory (also known as the Fill Rate).

2.        Why we should select the Type II as the service level
A Type I service objective is appropriate when a shortage occurrence has the same consequence independent of its time or amount. One example would be where a production line is stopped whether 1 unit or 100 units are short. The presupposition of this service, i.e., the same consequence ignoring the time or amount of a shortage occurrence, is not satisfied for most business scenarios. Also, as different items have different cycle lengths, this measure will not be consistent among different products, making the proper choice of this type difficult.

The term Fill Rate is often used to describe Type II service level, and is generally what most managers mean by service level. And the type is applied in most supply chain planning and inventory management products.

你说的probability 指的是probability of stocking out。 我说的probability指的是概率。
我所在的公司 对你说的probability of stocking out 简单成为stock out。

这就是我们的区别。

xuyongshuo

原帖由 icetea_cn 于 2008-7-22 10:07 发表
附件是MIT有关Inventory management课程中有关safety stock的部分。

看一下教程中的safety stock的计算，虽然考虑了fill rate，但也没有考虑提前期的波动吗。

其实不确定需求需要考虑的太多了，别太较真。没有哪个会将不确定因素考虑全的！如果非要计算全面，你是否还要考虑库存产品的合格率阿。具体情况具体应用就可以了，关键是解决主要矛盾。