Golden nugget 8: When you say “red”, what do you mean?

Dr. Eliyahu M. Goldratt

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Buffer Management and Drum-Buffer-Rope







When we are told that a production company has 20% red orders, what does that mean? Seemingly the answer is clear – it means that if we go to the floor, we will see that 20% of the orders are red. But then again, maybe it means something else – that out of all the completed orders, 20% were finished while being red? Here we have a situation where one term is being used to describe two different things. This ambiguity wouldn’t be a real problem if the practical implications, stemming from the two different interpretations, where the same. But this is definitely not the case; one of the above meanings of “red” is very important in terms of assessing the state of the operation, while the other has no practical implications and using it leads only to confusion. In order to clarify the above statement, we ought to better understand the meaning of each definition. The first definition of red percentage is a description of a snapshot – the situation on the floor at a certain moment: how many orders from each color do the production workers see? Figure 1.a schematically shows a distribution of orders’ color on the floor at a specific point of time, under the assumption of a constant stream of incoming orders. The X axis is not a time axis, but rather represents the “age” of an order at the point of time when the snapshot was taken