Six Sigma

Six Sigma ( 6σ ) is a management system for process improvement, statistical quality goal and also a method of quality management. Its core element is the description, measurement, analysis, improvement and monitoring of business processes using statistical methods. These often comes the Define - Measure - Analyze - Improve - Control ( DMAIC ) methodology used. The objectives are based on economically important financial parameters of the company and customer needs.

• 5.1 Expected error component at the Six Sigma level

Historical Development

The precursor of Six Sigma were introduced in the 1970s only in the Japanese shipbuilding and later in the Japanese electronics and consumer goods industries. Six Sigma was developed in 1987 by Motorola in the United States. 37

Large gained popularity of the Six Sigma approach by success at General Electric ( GE). Linked to this is the name of the manager Jack Welch, Six Sigma at GE introduced in 1996. In 2002, the International Society of Six Sigma Professionals ( ISSSP ) awarded him for it at the second ISSSP leadership conference, the ISSSP Premier Leader Award.

Today, many large companies are using Six Sigma - not only in manufacturing but also in services. Many of these companies expect their suppliers Evidence of Six Sigma quality in the production processes.

In product and process development area are modified DMAIC process and management processes are used, which are summarized under the term Design for Six Sigma ( DFSS, DMADV ). Also in the field of software development, there is a variant of Six Sigma.

Around since 2000, Six Sigma management is combined in many implementations, the methods of Lean and Lean Sigma or referred to as Lean Six Sigma and Six Sigma Lean.

As part of the sustainability discussion of process changes is increasingly since 2005, the process management (in terms of management of business processes in their daily business, but not primarily in terms of GPM - IT tool - topic ) complements the project methodologies DMAIC and DFSS an issue.

Roles and Responsibilities

Six Sigma improvement projects are led by specially trained staff. The introduction psychological concept of Six Sigma is based on role definitions that are based on the rank indicator ( belt color ) Japanese martial arts:

• The Deployment Champion is a member of the company's management; He is the driving force and advocate for Six Sigma in the company.
• The Master Black Belt is a full time improvement expert; it acts as a coach, trainer and instructor.
• The project champion (also project sponsor ) is usually a member of the middle management and clients for individual Six Sigma projects within the company. These managers are also often the process owner ( process owner ) for the process to be improved.
• The Black Belt is also working full-time as an improvement expert; he assumes project management responsibilities and has in-depth knowledge in the application of the various Six Sigma methods. The role of Black Belts Description provides for the implementation of four improvement projects per year, with a resulting reduction in spending of EUR 200,000 each before (depending on the size of the company ), as well as the parent company of about four other projects.
• The Green Belt is located in middle management - these are engineers, certified technicians, buyers, planners and masters who participate as team members on projects or conduct themselves under reporting to a Black Belt, smaller projects.

There are also depending on the company also " unofficial" belt colors (eg White Belts, Yellow Belts, Blue Belts ). These are located under the Green Belt and do not assume any project management tasks.

According to a general directive - quoted in many books - should be in the company per 100 employees a Black Belt active ( 1% BB- rule). A Master Black Belt should serve about 20 (experienced ) Black Belts. Then, for every Black Belt in turn about 20 Green Belts.

The Six Sigma Toolbox

As part of the DMAIC phases find a variety of quality techniques application that Six Sigma has taken over from the existing quality management practice. The following table provides an overview is:

The Six Sigma core process: DMAIC

The most commonly used Six Sigma methodology is the so-called " DMAIC " cycle ( Define - Measure - Analyze - Improve - Control = Define - Measure - Analyze - Improve - Control ). This is a project - and -loop approach. The DMAIC core process is used to already existing processes to make measurable and lasting improvements.

Define ( D)

In this phase of the process to be improved is identified, documented and described the problem with this process. This happens most often in the form of a Project Charter. This also includes:

• The desired goal state,
• The suspected causes of the current deviation from the goal state,
• The project definition (members, use of resources, scheduling )

In addition to the project charter usually more tools are used, such as:

• Problem definition using the Kepner -Tregoe analysis.
• SIPOC (Supplier, Input, Process, Output, Customer) - here is how the flow chart also, the process illustrated in order to get a better understanding of what happens within the process. This part also customer requirements (customer requirements ) to the output of the process and its requirements are applied to the inputs (Process Requirements) formulated.
• CTQ tree (Critical to Quality ) - description which measurable critical parameters are determinant for quality.
• VoC ( Voice of the Customer ) - method of a verbal customer problem (for example: "The device is difficult to use " ) to arrive at concrete targets for the elimination of the problem ( for example: " The device needs to each button a meaningful label in font size 12, the buttons must be arranged in a logical order. "). In the Define phase, the VoC is one of the most important tools since hereby it can be avoided that the customer is dissatisfied with the results in the end because he had other expectations.
• Scope In / Out Scope - The boundaries which aspects or areas of study component of the project should not be and what.

Measure ( M)

In this phase, it comes to determine how well the process really fulfill existing customer requirements. This involves a process capability analysis for each relevant quality characteristic.

Applied tools in this phase:

• Process visualization using process mapping,
• Statistical data collection and experimental design.

To ensure the measurement capability is used in Six Sigma, the so-called Measurement System Analysis (Measurement System Analysis ), short MSA.

Analysis ( A)

The aim of the analysis phase is to find out the causes for why the process not yet met the customer requirements to the extent desired. For this purpose, process analysis such as value-added, material flow or value stream analysis, and created data analyzes ( scatter). When you analyze data collected in the previous phase process or experimental data are analyzed using statistical methods, to identify the main scattering sources and to identify the root causes of the problem.

Applied tools in this phase:

• C & E matrix ( Causes & Effects) - Another tool for the preparation of the cause-effect hypotheses,
• By runtime analysis,
• Hypothesis testing,
• Ishikawa diagram - for determining the first hypotheses about cause-and- effect relationships,
• Pareto chart,
• Regression analysis,
• Scatter plot (Scatter Plot )
• Value-added analysis.

Improve (I ) (or Engineer (E ) for new processes)

Having understood how the process works, the improvement will be planned, tested and finally implemented. Here tools are applied, which are widely used outside of Six Sigma, for example:

• Place cipher method
• Knocked out analysis
• Criteria -based matrix
• Cost-benefit analysis
• Target process representation
• Poka Yoke
• Brainstorming and other creative techniques for generating ideas for solutions
• FMEA ( Failure Mode and Effects Analysis) - method of ascertaining the implementation risks of the improvement ideas

Control ( C)

The new process is monitored using statistical methods. This happens mostly with SPC control charts. In addition, other selected methods from the literature listed that are important for the sustainable maintenance of improvements, such as:

• Process documentation
• Process management - and response plan
• Precontrol
• Project success calculation.

The Six Sigma Roadmap shows a chronological guide to the use of the most important tools.

The cost of a DMAIC is high, so that the implementation only worthwhile if the expected value of the improved growth rates tend to process higher than 50.000 EUR. It strives for a project period of four to five months.

Six Sigma as a statistical quality objective

In most cases, it comes with every quality feature to unwanted scattering in the process results. Also, the average or mean value often does not lie exactly on the target value.

As part of a so-called process capability analysis such deviations from the ideal state are set in relation to the tolerance range of the relevant feature. The standard deviation of the feature plays (letter: σ; spoken: Sigma ) play a significant role. It measures the spread of the feature, ie the degree to vary the characteristic values ​​of each other.

The greater the standard deviation in comparison to the width of the tolerance range, the more likely to exceed the tolerance limits. Also speaking, the further the mean from the center of the tolerance range distance (ie the closer he draws near to a tolerance limits), the greater the proportion exceeded. Therefore, it is useful to measure the distance between the mean and the nearest tolerance limit in standard deviations. This distance divided by 3 σ is the process capability index Cpk; Thus, it is Cpk = 1 when the average is σ 3 from the closest of tolerance.

The name "Six Sigma" now is because at Six Sigma, the claim is made that the closest tolerance limit at least six standard deviations ( 6σ, pronounced in English "Six Sigma" ) to be the mean distance ( " Six Sigma Level " Cpk = 2). Only if this requirement is met, one can assume that virtually a " zero-defect production " is achieved, the tolerance limits are exceeded ie almost never.

Expected error component at the Six Sigma level

In calculating the expected error component is additionally contemplated that processes seen in practice over longer periods of observation, are exposed to unavoidable averaging fluctuations. It would be too optimistic to assume that the distance between the mean and the critical tolerance limit would be constant at 6 standard deviations. Based on practical observations, it has become the norm in the context of Six Sigma, a long-term mean shift einzukalkulieren by 1.5 standard deviations. If such a mean shift should actually occur, the average would be 6 instead of only 4.5 σ from the nearest tolerance limit removed.

Therefore, the excess portion of the " 6- σ level " of 3.4 DPMO ( Defects Per Million Opportunities, ie defects per million opportunities ) is specified. This corresponds to the most common type of distribution, normal distribution, the probability that a value occurs, which is different on the side nearest to the tolerance limit of at least 4.5 standard deviations from the mean, and thus exceed the tolerance limit. The following table lists DPMO values ​​for different sigma level; all these values ​​to calculate the mentioned mean shift of 1.5 σ a. Note that at the 3 σ DPMO value corresponds So, for example, the one-sided exceedance proportion of 1.5 σ, which corresponds to 4 σ the one-sided exceedance proportion of 2.5 σ, etc.

Success factors for the use of the Six Sigma methodology

The literature gives many critical success factors, which are listed below:

• Management integration - Since the introduction of Six Sigma is a strategic decision that counts the management support to the most important success factors. Even after the introduction of the long -term success depends heavily on the commitment of the management.
• Six Sigma methods knowledge - The Six Sigma method combines the well-known quality assurance methods and applies them in a systematic approach. In order to use this approach is a training of the staff required.
• Connection with the business strategy - The Six Sigma methodology has as primary goal to improve business results, while enhancing the customer's benefit. In the business strategy, the needs of consumers and businesses are connected.
• Connection to the customer - The Six Sigma methodology aims addition to improving the company's results from it, to increase customer satisfaction. For this, the customer claims must be known. Therefore, every Six Sigma project starts with an analysis of the external and internal customer requirements.
• Project Selection - The selection of promising projects with a view to the sustainable fulfillment of customer requirements at reduced costs is of particular importance. Also important is the measurability of qualitative improvements, as well as the detectability of the financial success. Also ensure that in the context of project selection on Projektrealisierbarkeit within a specified duration of the project.
• Organizational infrastructure - A supportive organization consisting inter alia of a sufficient number of belts, is imperative for a successful Six Sigma companies.
• Change in culture - Perennial Six Sigma application implies that the focus of pure cost reduction through to enhance customer value shifts.
• Project management skills of the Belts - As the Six Sigma methodology is based on successful project management, inter alia, are sufficient project management skills required to achieve a variety of milestones and goals.
• Connect to suppliers - The reason for the cooperation with key suppliers is that to transfer the improvements in the products and processes of the suppliers on the Six Sigma companies.
• Training of Belts in the Six Sigma methodology - For a successful Six Sigma implementation, it is important that a "critical mass " is reached at sufficiently trained employees.
• Connection to workforce planning - There are both requirements for the analytical- statistical thinking skills as well as on soft skills such as communication skills, teamwork and leadership ability to presuppose at the Belts.

Project Scope of Six Sigma projects

Six Sigma is implemented exclusively in the form of projects. The results of a Six Sigma program are the outcome of each project dependent. Therefore, the selection and the specific project work special attention must be paid. Direct responsibility for project results lies with the process owner. As a result, a careful project selection is critical.

The following rules for success / factors for the projects can be mentioned:

• Project duration: 3 to 6 months
• Project volume: large companies on average € 250 000, with medium-sized companies, on average, € 100 000
• Project framework: thematically and organizationally identifiable
• Process focus: it is an iterative process with a repetitive, measurable process output before

A survey following ranking for the selection criteria of Six Sigma projects can be seen:

• Annual cost savings: 68 %
• Process error rate: 66 %
• Customer Satisfaction: 44%
• Repeating Sequence: 34%
• Restricted scope: 28 %

One of the most common reasons for failures of Six Sigma projects is selecting the wrong projects. Especially with the first projects for the introduction of Six Sigma decides the success of a project on the success of the implementation of Six Sigma.

Six Sigma in the financial industry

In recent years, Six Sigma projects are being implemented throughout the financial industry is becoming more common. In the financial industry, there are a variety of processes (eg the pricing of financial instruments ) for which it is essential that they operate quickly and accurately. If this accuracy is not guaranteed, arise quickly unpleasant consequences with high follow-up costs (eg high tax reclaims ). Just errors in the master data and market data supply (eg an incorrect price feeds ) can quickly cause undesired direct and indirect costs. Possible effects would be, for example, hanging orders in the system, an incorrect price calculation or errors in reporting. As part of a Six Sigma project, the causes can be identified such problems and made ​​measurable. It can be developed individual solutions that lead to process optimization.