Читать книгу Lean Six Sigma For Dummies - Martin Brenig-Jones - Страница 23

So far so good, but without understanding the customer requirements, it’s not possible to tell whether cycle time performance is good or bad.

Let’s say the customer expects delivery in five days or less. In Lean Six Sigma speak, key customer requirements are called CTQs, (Critical To Quality). We discuss CTQs in Chapter 2 and describe them in more detail in Chapter 4, but essentially they express the customers’ requirements in a way that is measurable. CTQs are a vital element in Lean Six Sigma and provide the basis of your process measurement set. In our example, the CTQ is five days or less, but the average performance in Figure 1-2 is four days. Remember that this is the average; your customers experience the whole range of your performance.

Too many organizations use averages as a convenient way of making their performance sound better than it really is.

In the example provided, all the orders that take more than five days are defects for the customer in Six Sigma language. Orders that take five days or less meet the CTQ. We show this situation in Figure 1-5. We could express the performance as the percentage or proportion of orders processed within five days or we can work out the Process Sigma value. The Process Sigma value is calculated by looking at your performance against the customer requirement, the CTQ, and taking into account the number of defects involved where you fail to meet it (that is, all those cases that took more than five days).

We explain the Process Sigma calculation in the next section.