and completeness. We find 57 defects. With software, you can determine a precise process sigma value, but with the abridged table in Figure 1-6, find the sigma value that’s closest to your DPMO number of 38000. As you can see, this is 3.3.
© John Morgan and Martin Brenig-Jones
Figure 1-7: Calculating process sigma values.
A difference exists between process sigma and standard deviation (see the ‘Introducing a simple example’ section earlier in this chapter for how to work out standard deviations). This results from Motorola adjusting the tables to reflect the variation being experienced in its processes. This adjustment is referred to as a 1.5 sigma shift, reflecting the extent of the adjustment. Although this adjustment related to its processes, rightly or wrongly, everyone adopting Six Sigma has apparently also adopted the adjusted sigma scale. Incidentally, without this adjustment, Six Sigma would equate to 0.002 DPMO as opposed to 3.4 DPMO – so, even harder to achieve.
When we talk about Six Sigma performance before the adjustment, we’re talking about plus and minus six standard deviations, which embrace 99.999998 per cent of the data. And we are talking about the percentage of cases that are right first time in terms of meeting the requirements of the customer. Taking account of the adjustment, we’re still looking at a truly demanding standard, with 99.999666 per cent of cases right first time in meeting the CTQs.
The five key principles of Six Sigma are:
✔ Understand the CTQs of your customers and stakeholders. To deliver the best customer experience, you need to know what your customer wants – his requirements and expectations. You need to listen to and understand the voice of the customer (VOC), which we talk about in Chapter 4.
✔ Understand your organisation’s processes and ensure they reflect your customers’ CTQs. You need to know how your processes work and what they’re trying to achieve. A clear objective for each process should exist, focused on the customer requirements – the CTQs.
✔ Manage by fact and reduce variation. Measurement and management by fact enables more effective decision-making. By understanding variation, you can work out when and when not to take action.
✔ Involve and equip the people in the process. To be truly effective you need to equip the people in your organisation to be able, and to feel able, to challenge and improve their processes and the way they work.
✔ Undertake improvement activity in a systematic way. Working systematically helps you avoid jumping to conclusions and solutions. Six Sigma uses a system called DMAIC (Define, Measure, Analyse, Improve and Control) to improve existing processes. We cover DMAIC in Chapter 2. In designing new processes, we use DMADV.
Chapter 2
Understanding the Principles of Lean Six Sigma
In This Chapter
▶ Merging Lean and Six Sigma to make Lean Six Sigma
▶ Undertaking DMAIC to make things better
▶ Reviewing what you do in order to do it better
In this chapter we look at the synergy produced by combining the approaches of Lean and Six Sigma to form Lean Six Sigma. The merged approach provides a comprehensive set of principles, and supporting tools and techniques, to enable genuine improvements in both efficiency and effectiveness for organisations.
Considering the Key Principles of Lean Six Sigma
Lean Six Sigma takes the features of Lean and of Six Sigma and integrates them to form a magnificent seven set of principles. The principles of each approach aren’t dissimilar (check out Chapter 1 to read more about the individual components), and the merged set produces no surprises. The seven principles of Lean Six Sigma are:
✔ Focus on the customer. The customer’s CTQs describe elements of your service or offering they consider Critical To Quality (see Chapter 1 for more on these). Written in a way that ensures they’re measurable, the CTQs provide the basis for determining the process measures you need to help you understand how well you perform against these critical requirements. Focusing on the customer and the concept of value-add is important because typically only 10–15 per cent of process steps add value and often represent only 1 per cent of the total process time. These figures may be surprising, but they should grab your attention and help you realise the potential waste that’s happening in your own organisation. As you improve your performance in meeting the CTQs, you’re also likely to win and retain further business and increase your market share. The concept of value-added process steps is covered in Chapter 9, and Chapters 3 to 5 consider the customer in more detail.
✔ Identify and understand how the work gets done. The value stream describes all of the steps in your process – for example, from a customer order to the issue of a product or the delivery of a service, through to payment. By drawing a map of the value stream, you can highlight the non-value-added steps and areas of waste and ensure the process focuses on meeting the CTQs and adding value. To undertake this process properly, you must ‘go to the Gemba’. The Japanese word Gemba means the place where the work gets done – where the action is – which is where management begins. Process stapling (which we introduce in Chapter 5) involves you spending time in the workplace to see how the work really gets done, not how you think it gets done or how you’d like it to be done. You see the real process being carried out and collect data on what’s happening. Process stapling helps you analyse the problems that you want to tackle and determine a more effective solution for your day-to-day activities.
✔ Manage, improve and smooth the process flow. This concept provides an example of different thinking. If possible, use single piece flow, moving away from batches, or at least reducing batch sizes. Either way, identify the non-value-added steps in the process and try to remove them – certainly look to ensure they do not delay value-adding steps. The concept of pull, not push (see Chapter 1), links to your understanding the process and improving flow. And it can be an essential element in avoiding bottlenecks. Overproduction or pushing things through too early is a waste.
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