Six Sigma DMAIC Methodology
Nowadays enterprises have started to practice lean and six sigma concept. These article describes the six sigma and its advantages and disadvantages. DMAIC (Define, Measure, Analyze, Improve, & Control) model has been used to implement the Six Sigma Philosophy. Five phases of DMAIC Method are detailed in this paper. Organizations use at six sigma methodology utilize trained specially individuals, called Green Belt, Black Belt and Master Black Belt. This paper presents a short brief a belt system used in six sigma project.
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Six sigma is the one of the most effective and familiar process improvement methodology in recent years. Its origin is traced back to the pioneering and innovation work done at Motorola and its spread by many companies including GE, Ford, General Motors, etc.
Six Sigma Methodology has two perspectives; statistical and business viewpoint. The origin of six sigma comes from statistics and statisticians. From the statistical point of view, the term six sigma is defined as having less than 3.4 defects per million opportunities or a success rate of 99.9997% where sigma is a term used to represent the variation about the process average . In the business world, six sigma is defined as a ‘business strategy used to improve business profitability, to improve the effectiveness and efficiency of all operations to meet or exceed customer’s needs and expectations 
The objective of this article is to define the six sigma with its origin and describes the advantages and disadvantages. The paper also summarizes the DMAIC cycle with tools;
The belt system in which six sigma practitioners receive special training is also described in this article. These belts are based on level of competence in understanding and applying related tools:
Green belt: This green belt is a basic analytical tools, it will be works on less complex projects
Black belt: In this black belt emphasis on application and analysis, work projects with help from green belts.
Master Black belt : It is mainly used to understand applications and statistical theory behind applications, trains other belts, and leads project reviews.
What is Six Sigma?
Six Sigma is a systematic methodology aimed at operational excellence through continuous process improvements . Sigma ϭ is the letter in the Greek alphabet used to denote standard deviation, a statistical measurement of variation, the exceptions to expected outcomes. Standard deviation can be thought of as a comparison between expected results or outcomes in a group of operations, versus those that fail. The measurement of standard deviation shows us that rates of defects, or exceptions, are measurable. Six Sigma is the definition of outcomes as close as possible to perfection. With six standard deviations, we arrive at 3.4 defects per million opportunities, or 99.9997 percent. This would mean that at Six Sigma, an airline would lose only three pieces of luggage for every one million that it handles; or that the phone company would have only three unhappy customers out of every one million who use the phone that day. The purpose in evaluating defects is not to eliminate them entirely, but to strive for improvement to the highest possible level that we can achieve. 
A company’s performance is measured by the sigma level of their business processes. The Six Sigma standard of 3.4 problems-per-million opportunities is a response to the increasing expectations of customers and the increased complexity of modern products and processes .
We know that trying to achieve Six Sigma would be impractical on a consistent basis; so while it is a desirable goal, it presents a model against which we can measure our performance. So rather than setting the unrealistic goal of achieving perfection, we can observe our current Sigma level and improvement in that level as changes are made.
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Table 1 presents an abbreviated summary of Sigma level, defects per million, and yield, or success rate of the outcomes . You can identify your level of Sigma performance and then compare it to the chart. This is where the benefits of Six Sigma are realized. By comparing your outcomes to the ideal outcome of Six Sigma, you can quantify quality itself.
Origin of Six Sigma
Bill Smith, a Motorola engineer, developed the Six Sigma programme in 1986 as a response to the necessity for improving quality and reducing defects in their products. The CEO, Bob Galvin, was impressed by the early successes, and under his leadership, Motorola began to apply Six Sigma across the organization, focusing on manufacturing processes and systems. Godfrey (2002) interviewed Bob Galvin on these early days of Six Sigma.
Motorola established Six Sigma as both an objective for the corporation and as a focal point for process and product quality improvement efforts. The Six Sigma concept was tremendously successful at Motorola. It has been estimated that they reduced defects on semiconductor devices by 94% between 1987 and 1993. In recent years, Six Sigma has spread beyond Motorola and has become a programme for improving corporate business performance by both improving quality, reducing costs and expanding markets for products and services. Six Sigma, in some form, has been adopted by thousands of companies both large and small. 
Advantages of Six Sigma
- Six Sigma quality refers to having 3.4 defects per million opportunities or product samples.
- Six Sigma is driven by the customer and thus aims to achieve maximum customer satisfaction and minimizing the defects. It targets the customer delight and new innovative ways to exceed the customer expectations.
- Implementation of Six Sigma methodology leads to rise of profitability and reduction in costs. Thus improvements achieved are directly related to financial results.
- Six Sigma is successfully implemented in virtually every business category including return on sales, return on investment, employment growth and stock value growth.
- Six Sigma targets Variation in the processes and focuses on the process improvement rather than final outcome.
- Six Sigma is prospective methodology as compared to other quality programs as it focuses on prevention on defects rather than fixing it.
- It is attentive to the entire business processes and training is integral to the management system where the top down approach ensures that every good thing is capitalized and every bad thing is quickly removed.
- Adopting Six Sigma process improvement puts in place a continual process improvement methodology at all levels of an organization. Once Six Sigma is embedded in a corporate culture, the business processes will continue to improve. Furthermore, new problems will be quickly identified and corrected due to the close monitoring Six Sigma entails.
- By focusing on defect prevention over fixing defects, companies can realize major and continuing savings over prior rework, scrap and return costs.
- Six Sigma is data driven. No changes are made until the current process is thoroughly understood, documented and measured. The revised process is similarly measured and verified. If the Six Sigma project does not deliver what was intended, the Six Sigma team is still there to correct new found problems or study what went wrong. 
Disadvantages of Six Sigma
- Six Sigma projects may not yield any cost savings at all. Improving product quality can generate capital costs and long term overhead costs in terms of more quality personnel.
- As product quality improves, tighter quality standards may be adopted or the process is left as it is but closely supervised. Yet data collection and analysis takes up time and resources; this is called the cost of quality, and the cost of achieving high quality must be balanced against other business objectives.
- Six Sigma does not work well with intangible results. Six Sigma projects are best for physical products that are out of specification, either too large or too small.
- Six Sigma projects can be applied to business processes that generate measurable outputs such as calls handled per hour or customer wait time. Six Sigma projects do not work well with goals like improving customer satisfaction or lifting employee morale.
- When Six Sigma process methodology is applied to business processes such as performance reviews or processing purchase orders, the recommended solution is often called “bureaucracy busting”. This can result in push-back from management afraid of losing their jobs.
- Six Sigma implementation constantly require skilled man force. Thus control and employee dedication are hard to accomplish if its not implemented regularly.
- While converting the theoretical concepts into practical applications there are lot to real time barriers which needs to be resolved.
- Six Sigma gives emphasis on the rigidity of the process which basically contradicts the innovation and kills the creativity. 
Companies involved in a Six Sigma effort utilize specially trained individuals, called Green Belts (GBs), Black Belts (BBs), and Master Black Belts (MBBs). 
The assignment of belt colors to various roles is derived from the obvious source, martial arts. At the top of the achievement level in karate, for example, is the Black Belt. The person possessing this belt has achieved the highest skill level and is an experienced expert in various techniques. As applied to the Six Sigma program, the individual designated as a Black Belt will have completed a thorough internal training program and have experienced work on several projects. The black belt holder is usually given the role of team leader, the person who is responsible for execution and scheduling . In most organizations, BBs train GBs and work on other functions such as new project identification. The “belts”, particularly BBs and MBBs, have specialized training and education on statistical methods and other quality and process improvement tools that equip them to function as team leaders, facilitators, and technical problem solvers. 
Another level is the Master Black Belt, a person who is available to consult with the team or its leadership but who is not a direct member of the team itself. This may be the equivalent of the role played by the coach; or for more technical and complex projects, the Master Black Belt is available to answer procedural questions and to resolve the technical issues that come up. The Green Belt designation can also belong to the team leader or to a member of the team working directly with the team leader. Referring back to the source designations, a karate green belt is less experienced than the black belt but is cast in a key role within the team. These colorful names were originally intended to add a descriptive sense to the otherwise dry roles of leader, sponsor, and other well-known but overused corporate titles. The advantage of describing a role or series of responsibilities in terms of belt colors may be helpful in exhibiting an individual’s team experience and ability. The distinction between the actual designation and the belt color should not confuse the roles played by each participant on the team. 
Six Sigma uses a specific five-step problem-solving approach: Define-Measure-Analyze-Improve-Control (DMAIC.) The DMAIC framework utilizes control charts, designed experiments, process capability analysis, measurement systems capability studies, and many other basic statistical tools. The DMAIC approach is an extremely effective framework for improving processes. 
DMAIC is described briefly as follows:
D Define the goals of the improvement activity.
M Measure the existing system.
A Analyze the system to identify ways to eliminate the gap between the current performance of the system or process and the desired goal.
I Improve the system.
C Control the new system. 
- Define Phase
This phase defines the project. It identifies customer CTQs and ties them to business needs. Further, it defines a project charter and the business process bounded by the project .
- Measure Phase
This phase is concerned with selecting one or more product characteristics (dependent variables), mapping the respective process, making sure the measurement system is valid, making the necessary measurements, and recording the results, 
- Analyze Phase
This phase entails estimating the short and long-term process capability and benchmarking the key product performance metrics. Following this, a gap analysis is often undertaken to identify the common factors of successful performance; that is, what factors explain best-in-class performance. In some cases, it is necessary to redesign the product and/ or process. 
- Improve Phase
This phase is usually initiated by selecting those product performance characteristics that must be improved to achieve the goal. Once this is done, the characteristics are diagnosed to reveal the major sources of variation. Next, the key process variables are identified by way of statistically designed experiments. For each process variable that proves to be significant, new or improved processes are developed to bring performance within customer requirements. These improvements are tested/piloted to confirm their capability. Then they are documented. 
- Control Phase
This phase is related to ensuring that the new process works in the organization after project closure and formal transfer of the solution back to the process owner. Measurement systems are validated and statistical process control methods identified. The new process capability is assessed and compared to Project goals. It may be necessary to revisit one or more of the preceding phases if they fall short. Improvement retention measures are developed and the process is transitioned/returned to the process owner. Project administration is completed and the team is disbanded. These phases are summarized in Figure 7 and laid out in a little more detail in Figure 8. 
Six sigma – DMAIC methodology has been successfully implemented in all processes over 30 years. This paper presents the six sigma – DMAIC methodology definitions with the related tools. As a summary, six sigma is a philosophy of reducing variation in process to achieve continuous improvement and uses define- measure-analyze-improve and control (DMAIC) methodology for problem solving with a special tool and statistical techniques.
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Ayça Gürel – Quality Assurance Engineer