1. Building the Foundation for Six Sigma – Six Sigma for Business Excellence: Approach, Tools and Applications


Building the Foundation for Six Sigma

The Evolution of Six Sigma

Six Sigma is one of the most popular approaches embraced by companies all over the world during the last two decades to achieve business excellence. The primary objective of Six Sigma is to reduce variation, in products or processes, to achieve quality levels of less than 3.4 defects per million opportunities (DPMO). The Six Sigma approach, now a model for business excellence, is deployed by many world-class companies to make breakthrough improvements that directly lead to improved financials.

The Six Sigma approach was first introduced and developed at Motorola in the late 1980s. Motorola learned about quality the hard way, being consistently beaten as it was in the competitive marketplace (Pyzdek 2003). A Japanese firm took over a Motorola factory which made television sets in the United States. The new management improved the quality performance and reduced the defect level of the TV Sets to 1/20th of the level that had been under the previous management.

The top management of Motorola realized the urgent need to improve their quality performance and reputation. In 1986, Bill Smith, a senior engineer and scientist with Motorola's Communications Division, introduced the concept of Six Sigma in response to increasing complaints from the field sales force about warranty claims. Bill approached Bob Galvin, the CEO at the time, and explained his analysis and ideas about the Six Sigma approach. Bob recognized the power of the approach and decided to adapt it for Motorola (McCarty 2004).

Bill Smith is known as the “Father of Six Sigma” (Chadwick 2000). Born in Brooklyn, New York, Smith graduated from the US Naval Academy in 1952 and studied at the University of Minnesota School of Management (now known as the Carlson School of Management). While Six Sigma was developed at Motorola, the concepts, approach and tools evolved gradually through the knowledge, experience and wisdom of many quality experts and statisticians. Before Six Sigma was born, industry had tried and tested Total Quality Management (TQM). Many companies had significant success with TQM. The roots of Six Sigma can, therefore, be traced back to the philosophies of many quality gurus, philosophies that were part of the TQM approach as well. While it is impossible to include all contributions, the most prominent ones are shown in Figure 1.1.

Soon after implementing Six Sigma, Motorola received the coveted Malcolm Baldrige National Quality Award (MBNQA) for business excellence. Later, in the mid-1990s, Six Sigma was adapted by Allied Signal and General Electric (GE). According to Jack Welch, CEO of GE, “Six Sigma is the most challenging and potentially rewarding strategy GE has ever undertaken” (2001). The company listed tremendous benefits of the approach in their annual report in 1997. These benefits included the following points:



Figure 1.1 The contribution of quality gurus to the evolution of Six Sigma


  • Ten-fold increase in the life of CT scanner X-ray tubes in their medical devices section
  • Improved yield resulting in increased capacity without additional investments at Superabrasives—their industrial diamond business
  • Sixty-two percent reduction in turnaround time at the repair shops of their railcar leasing business
  • Addition of 300 million pounds worth of new capacity. This was equivalent to adding a new plant.

At General Electric, significant portions of the company's bonuses were linked to the introduction of Six Sigma. This approach was originally deployed for bringing about improvements in manufacturing, probably because the manufacturing industry had better knowledge of the statistical tools and benefits could be quantified easily. However, as these improvements were not directly visible to the customer, the approach was broadened to include all business operations. The success of the companies adapting the Six Sigma approach caught the attention of the Wall Street making it a popular strategy that is being adapted by many organizations worldwide. Many other companies such as Allied Signal, Du Pont, Ford, General Motors, and Cummins embraced the Six Sigma approach after its early success.

Some reputed Indian organizations such as Cummins India Limited, SKF, Reliance, Wipro, Hero Motors, Godrej-GE, Infosys, HDFC, Indian Petrochemicals Limited (IPCL), and UCAL Fuel have also adapted Six Sigma to improve their businesses. One of the most cited examples of Six Sigma quality is Mumbai's Dabbawala or tiffinwallas or dabbawallas as they are called in the local language. Most of the tiffinwallas, though illiterate, have an amazing passion, dedication and zest for innovation—qualities that have led them to achieve a level which is nearly 6.5 Sigma or better. They have demonstrated to the quality professionals that these traits are far more critical than statistical and other tools to achieve Six Sigma (Bondre 2006).

What Is Six Sigma?

Six Sigma is a highly disciplined approach used to reduce the process variation to such a great extent that the level of defects is drastically reduced to less than 3.4 per million process, product or service opportunities. The approach relies heavily on statistical tools which, though known earlier, were primarily limited to use by statisticians and quality professionals.

Sigma (σ) is a letter of Greek alphabet that is used to describe variability. In statistical quality control, this denotes standard deviation. Defect level is measured in terms of parts per million (PPM) or defects per million opportunities (DPMO). We will see later how PPM or DPMO level of 3.4 is actually calculated. Figure 1.2 shows the PPM as a function of sigma level.


Figure 1.2 Sigma level, illustration of 1.5 sigma shift and DPMO


Note: LSL and USL stand for lower specification limit and upper specification limit respectively.
(Courtesy Institute of Quality and Reliability, Pune)


PPM levels are calculated mathematically with normal distribution. The term PPM is sometimes replaced by DPMO. We will separately discuss the calculation of DPMO in Chapter 4 which is about basic statistical concepts. We must not consider these as precise figures but as indicative DPMO levels that drive breakthrough improvements. We can see from the graph that moving from 3 to 4 sigma level is a 10-fold improvement; from 4 to 5 sigma level, it is a 27-fold improvement; and moving from 5 to 6 sigma level, the improvement is 67-fold! In reality, it is extremely difficult to reach a 6 sigma level in all the processes and products in a company. Six Sigma should, therefore, be considered as an approach for improvement rather than a statistical metric.

DPMO and Sigma Level

A defect need not necessarily be only in a product. It can show up in a service as well. For example, if customers expect that a part be delivered within one day of the committed delivery date, then even if it is delivered just one day after that, it is a defect for them. What customers expect from a product or service can be considered as “critical to quality” or CTQ. Quality is the ability of a product or service to fulfill customers’ requirements. Joseph Juran defined quality as “fitness for use”; Phillip Crosby defined it as “conformance to specifications”.

Defects can show up in a number of forms. Some examples are given below:

  • While checking-in at the airport, a passenger holding a confirmed ticket for a flight finds that his name is missing in the list of passengers
  • A customer finds the switch of a remote control unit sticky
  • The DVD drive of a new laptop is repaired thrice and yet it fails to function
  • A customer's name is printed wrong on the telephone bill
  • A vehicle does not meet the regulatory requirement for emissions.

These are not mere examples but my personal experiences. The new laptop problem was the most expensive for me and also for the company. I lost at least 5 of my workdays. Worse still, the company informed me that the laptop was registered in some other name. I had to send the scanned copy of the receipt to prove that I was the real owner. Finally, I had to reinstall the operating system—a nightmare in itself. Thus defects result in to a loss to the customer as well as to the product or service provider. Sometimes, additionally, defects could cause a loss to the society. This is called the “cost of poor quality” (COPQ).

Another interesting example that is not often discussed is the number of service updates or patches released to correct bugs in any software. This is so routinely done that it has come to be accepted as a norm. When customers buy any software, they would expect it to be backward compatible. We all know that most users were reluctant to use Windows Vista as they were worried that older software would not work with it. While writing this, I counted more than 100 updates to the Vista on my laptop; although many of these are security updates. I don't intend to criticize any particular company here, I nonetheless want to share my views on what the customer is likely to consider as defect. A product or service may have not just one but many opportunities for defect. For example, a mobile phone can have 10 different types of defects which can be considered as opportunities for defects.

Practical Meaning of Sigma Level

Let us consider a few examples of Six Sigma quality level.

  1. In India, 14,444 trains run everyday. Passengers expect these trains to reach on time. For the sake of simplicity, let us consider each train as an opportunity for arriving late every day at the final destination. Thus, there are, in total, 365 × 14,444 = 52,72,060 opportunities in a year. At Six Sigma quality level, there can be a maximum of 3.4 defects per million opportunities (DPMO). Hence, for 52,72,060 opportunities, the number of late trains will be Thus, if Indian Railways reaches the Six Sigma quality level for timeliness (let us hope so!), they will have, at the most, 18 trains arriving late in the whole year. We can make a more precise calculation by considering timely arrival at each station as one opportunity, but that would only make our calculations more complicated.
  2. Here is another example. In the case of bank transactions, customers expect that they should get a complete set of documents within three days of submitting their application to open an account. Any customer who gets the documents after three days considers this to be a defect. A particular bank opens a total of 5000 accounts in three months. Its past three months’ data show that in 125 cases, they missed the target of three days. Hence, their defect level per million can be calculated as

This corresponds to a sigma level of 3.46 for the account opening period. Calculation of sigma level is explained in Chapter 7, “Process Capability and Sigma Level”. Figure 1.3 shows the calculation of sigma level using the Sigma Calculator template provided in the CD. Alternately, you can use Table T7 of sigma level vs defects per unit provided in the CD.

Business Model and Stakeholders

While the objective of any business is to make profit, its existence depends primarily on its customers. Each business has its own processes and systems. A process converts an input into a form that is of value to customers. This applies equally to all businesses—from the simplest to the most complex.


Figure 1.3 Sigma level calculation for bank


(Courtesy Institute of Quality and Reliability, Pune)



Figure 1.4 Business process


In a simple business like a retail shop, the shopkeeper stocks items that customers want to buy for use. If retail shops did not exist, customers would have to commute to wholesalers to buy these items. Thus, here the value addition is making the items available at a location convenient to the customers. In return, the retail shop charges a higher price than the wholesaler. In a complex process like manufacturing automobiles, the company may have a large number of suppliers of engines, transmissions, pumps, wheels, etc. The company understands the needs of its customers and designs and manufactures automobiles to meet these needs. The company will, therefore, need people and systems to perform the following functions:

  • Marketing, to understand the needs of customers and to identify markets which would be profitable
  • Design and development processes to convert customers’ expectations into a product
  • Manufacturing infrastructure and processes to produce the designed parts and assemblies
  • Supplier development processes to source parts which the company does not want to or cannot manufacture in-house
  • Sales and distribution network and processes to ensure that customers get what they ordered
  • Servicing infrastructure, network and processes to repair any product that fails during usage due to manufacturing defects, wear and tear or customer misuse
  • Accounting processes to ensure that the financial transactions are timely and accurately recorded so that information critical to business is available quickly and easily
  • Finance processes to ensure that capital is available and shareholders get adequate return on the capital.

The above functions are typical to a manufacturing company. Functions for software or other service-oriented companies can be listed in a similar manner. The list is by no means comprehensive but is just an illustration, indicative of the nature of business systems.

In the prevailing scenario, business quality is decided not merely by the customer but by all the stakeholders. There are various stakeholders with different expectations from the business:

  1. Customers expect good quality, a reliable product (or service) at a reasonable price at the committed time. In case of a service, the time element usually holds more importance than in the case of tangible products.
  2. Shareholders expect a good return on their invested capital.
  3. Employees expect a good career with the company, good salary, work environment, work culture, recognition of their contribution, etc.
  4. Government and regulatory agencies expect timely payment of taxes, compliance with regulations, etc.
  5. Society expects contribution to the overall well-being of the society and to other activities/events.

All the above aspects are often interleaved or interdependent and hence good companies evolve their business strategy considering all of these stakeholders. For example, employee satisfaction has an important impact on customer satisfaction. Customer as well as investor confidence is essential for sustainable business. Non-compliance with government regulations can lead to business disruptions and difficulties. Adverse relations with the society can affect customer preference, loyalty of employees and overall goodwill for the company.

Six Sigma for Business Excellence

Business excellence can be achieved by having “quality in every process” of the company with the objective of meeting expectations of customers and all other stakeholders. Processes are managed efficiently to minimize waste and to assure compliance with the “Right First Time, Every Time” rule. Business excellence is often perceived as near perfection in various business processes. It is not limited to products and services but also encompasses processes that affect other stakeholders, i.e., employees, shareholders, suppliers, society, and government. Some examples of business excellence can be in the cases described below:

  • Every employee retiring from a company gets gratuity payment on his/her last working day without having to ask for it.
  • Financial statements are published almost immediately after the stipulated period.
  • The company makes it a point to concern itself with the social and environmental impacts of its operations.
  • It believes in high ethical standards and corporate governance.

To achieve business excellence, Six Sigma should address the gaps and weaknesses in satisfying the expectations of all stakeholders. Thus, the focus of Six Sigma implementation should be decided based on inputs from various stakeholders.

There are different approaches to achieving business excellence which have been tried by various companies. Some of these approaches are listed here.

  • TQM
  • Total productive maintenance (TPM)
  • Kaizen
  • Balanced scorecard
  • Lean manufacturing

Six Sigma has some overlap with all these approaches. It can blend very well with Lean and also with the balanced scorecard approach. TPM can be considered as supportive to Six Sigma to improve productivity, delivery performance and to reduce costs. Lean Six Sigma (sometimes called Lean Sigma) combines the two approaches with a focus on reducing cycle times and waste. Important elements of TQM are customer satisfaction, continuous improvement in all processes, statistical process control. We may consider Six Sigma as a “specific approach of TQM”.

Kaizen is adapted by companies to involve everyone in the improvement activities. Kaizen can be considered as large number of small projects whereas Six Sigma is a small number of large projects. Project selection in Six Sigma follows a top-down approach whereas Kaizen often follows a down-to-top approach. Balanced scorecard is an excellent system to continually feed projects to the Six Sigma belts.

A senior vice president of a multinational corporation (MNC) once asked me what level of 5S they should achieve before taking up the Six Sigma initiative. ‘Five S’ is an approach that involves organizing the workplace to minimize waste and is usually a part of Kaizen. It is called 5S to denote the five key steps Seiri-Seiton-Seiso-Seiketsu-Shitsuke which are Japanese words starting with the letter s. (For more information on 5S, refer to Chapter 19.) My suggestion to him was to achieve a satisfactory level of 5S, a level at which mistakes can be prevented. Housekeeping is important to minimize waste. However, it cannot be useful for improving process parameters. In Six Sigma, we want to reduce variation. If poor housekeeping results in large variation, we better take up housekeeping improvement as a priority before moving on to Six Sigma.

There are business excellence models such as Malcolm Baldrige National Quality Award (MBNQA) in the US, European Quality Award (EQA), Rajiv Gandhi National Quality Award (RGNQA) in India. These models, termed as quality awards, also require demonstration of excellence in all aspects of business, not only in product and service quality. Some of the striking differences in Six Sigma as compared to other approaches are given below:

  • Clear and direct linkage of projects to financial benefits
  • Careful selection of the best people to learn and implement Six Sigma
  • Comprehensive training in Six Sigma tools
  • Immediate application of the Six Sigma tools to projects.

Training in many tools did exist earlier but Six Sigma makes it mandatory for the belts to apply these tools and also to demonstrate improvements.

Six Sigma and Lean

Lean aims at increasing the speed by eliminating waste in the system. Six Sigma is aimed at reducing variation to improve the process quality. These two seemingly different approaches are actually very strongly related. For example, if we want to reduce the work in process inventory, we need to synchronize the flow and produce when the customer “pulls” or demands. If we want to make this happen, we must make the process very predictable. A predictable process requires high process capability that produces parts without any defects. To achieve this, we must apply the Six Sigma tools to minimize variation. Poor quality levels of processes can result in significant increase in inventory and can adversely affect delivery performance, thereby leading to customer dissatisfaction. According to Michael George, a lean Six Sigma expert, 10 percent scrap can slow down a process by 40 percent (George 2002).

Companies that implement Six Sigma only may not be able to reduce cycle times or inventories. Most of the Six Sigma tools do not focus on time; the objective in Six Sigma is to eliminate defects. For customers, time is one of the important elements of their expectations. A part perfectly manufactured but delivered late may not be acceptable to them. Defect reduction, no doubt, is important to reduce cycle time. However, there are many other non-value-added activities/elements such as set-up times, machine breakdowns, transportation, etc. that must be minimized or eliminated to increase process speed. The companies need to apply the Lean philosophy of eliminating non-value-added activities so that the process-cycle efficiency improves. Dramatic improvements are possible when they implement Lean and Six Sigma together.

At GE, when Jack Welch realized that customers are not experiencing benefits of Six Sigma, he introduced a concept of “span” which is actually variation of delivery around committed date (Welch 2001). Span is described as a measurement of operational reliability. It is the “time window around the customer-requested delivery date in which delivery will happen”.

Michael George defines Lean Six Sigma as “a methodology that maximizes shareholder value by achieving the fastest rate of improvement in customer satisfaction, cost, quality, process speed and invested capital”. One of the important principles of Lean Six Sigma is that “the activities that cause hindrances in customer's critical-to-quality (CTQ) requirements and create the longest time delays in any process offer the greatest opportunity for improvement”.

Let us take a look at the questions that Lean Six Sigma can uniquely answer.

  • Which process steps should be prioritized for improvement?
  • In which order and to what degree?
  • How do we get the biggest cost, quality and lead time improvements quickly?

Table 1.1 shows some typical tools used in the Lean Six Sigma projects, especially to reduce waste, lead time and/or cycle time. The stages at which the tools are used are only indicative and could vary in practice.


Table 1.1 Typical tools used in Lean Six Sigma projects


Lean philosophy and tools are discussed in detail in Chapter 19.

Six Sigma and Kaizen

Six Sigma and Kaizen events should be distinguished clearly. Kaizen is a philosophy of continuous improvement whereas Six Sigma is an approach towards breakthrough improvements.

  • Kaizen is participative. Each employee can participate and is encouraged to make suggestions for improvement. Each of these suggestions is a potential Kaizen event. According to Masaki Imai, the father of Kaizen, suggestions and ideas for improvement from those involved in the process can be very useful and motivating. Six Sigma, on the other hand, is primarily implemented by black belts, green belts and their team members.
  • Kaizen events usually cost less and focus on people involvement. Six Sigma projects can cost more as black belts or green belts spend significant time on the projects.
  • Kaizen encompasses many simple tools; hence, these can be applied with little training. However, even though these tools are simple, they can still solve a large number of problems. Many Six Sigma tools are somewhat complex and require sophisticated software. Hence, the use of these tools can be taught to only few educated individuals who have such capability.
  • Kaizen is quite often considered as an initiative for cultural transformation as everyone is expected to get involved. Six Sigma is also aimed at cultural transformation but the value of Six Sigma projects is measured typically in financial benefits.
  • The number of Kaizens in a company can easily be a few thousand. The number of Six Sigma projects is usually much lower.

Both Kaizen and Six Sigma have their own benefits. Executive leadership and the steering committee should evaluate which of the approaches is appropriate for their company. Sometimes, both Kaizen and Six Sigma initiatives are simultaneously implemented. This can be taxing for key resources as these could be common.

Projects with higher complexity require the use of Six Sigma tools. For simpler projects, Kaizen can be adopted and implemented by the operating personnel who run the process. Some of the simpler Kaizens may result in significantly large benefits. These could be low-hanging fruits. Projects aiming at higher benefits are likely to be more difficult, although this cannot be generalized.

Six Sigma and Quality Certifications

It is sometimes forgotten that a company should have done the basic groundwork by implementing a quality system such as QS–9000 or ISO TS 16949 or at least ISO 9000. One cannot move on to graduation without getting through the steps of secondary school exams. Six Sigma methodology helps in the identification of cause and effects relationships between results (‘Y's) and factors (‘X's). Some of these relationships may be already known through documented wisdom in the form of quality assurance standards. It is expensive to reinvent this using Six Sigma. For example, a company obviously needs to have a system for drawing and specification control, calibration of measuring and test equipment, training people, adequate work instructions, supplier quality assurance, etc. If Six Sigma is deployed to prove that these factors affect quality, it will be a waste of time and money.

Fortunately or unfortunately, there is no international standard of Six Sigma certifications for companies. Motivation for Six Sigma comes from the senior management, i.e., from within the organization. Sometimes, customers impose implementation of Six Sigma on their suppliers. The backbone of a successful Six Sigma implementation is strong commitment of the top management. Since there are no international standards, it is expected that there will be differences in Six Sigma approaches among companies adopting the Six Sigma philosophy. However, there are many commonalities which can be seen across most companies. These are

  • Project-based improvement approach
  • Strong linkage to business goals, objectives and financial benefits
  • Projects sponsored by senior management
  • Execution of projects by leaders called black or green belts
  • Extensive training in statistical tools
  • Projects across various functions and not usually limited to product quality.
The Six Sigma Methodology

Six Sigma is a project-based approach. Projects that have a sizable impact on customer satisfaction and significant impact on the bottom line are selected. The senior management of an organization has a very important role to play in the selection of projects and leaders. The projects must be clearly defined in terms of expected key deliverables. These are typically in terms of PPM levels or sigma quality levels, number of customer complaints, cycle times, warranty failures, rejection levels, employee satisfaction index, supplier delivery performance, transaction accuracy, cycle times, etc.



Figure 1.5 From practical problem to practical solution


In the typical approach used in Six Sigma for process improvement, the actual problem is first converted into a statistical problem. This is done by mapping the process, defining key process input variables (KPIVs or ‘X's) and key process output variables (KPOVs or ‘Y's). The power of statistical and other tools is used to determine a statistical solution. This is then converted into a practical solution.

The Roadmap for Process Six Sigma

This is the most popular model of Six Sigma. The focus is on improvement of business processes and solving problems. Process Six Sigma projects go through five phases:

  1. Define what needs to be improved.
  2. Measure current performance and the gap with respect to desired target.
  3. Analyze the processes to find the root cause of the problem.
  4. Improve Select a solution and implement.
  5. Control the process parameters to assure and sustain improvement.

As shown in Figure 1.6, many of the input factors i.e. ‘x's get eliminated through the use of various statistical and other tools. This is as if the variation is getting reduced as it passes through a funnel of the Six Sigma methodology. This is sometimes called the breakthrough strategy.

A Brief Overview of DMAIC Roadmap

The Six Sigma methodology can be considered as a funnel that reduces variation and waste. The DMAIC roadmap is briefly explained below:


Figure 1.6 Six Sigma roadmap and tools


(Courtesy Institute of Quality and Reliability, Pune)

  1. Define

    The key actions in the define phase are

    • Identify opportunities for improvement.
      • The senior management plays a key role in the process.
      • Characteristics that are critical to quality must be listed based on surveys, quality cost data, rejections, delivery performance, employee satisfaction, market share, business goals and aspirations.
    • Prioritize project ideas.
      • Ensure that projects are strongly linked to customer expectations, stakeholders’ expectations and business objectives.
      • Use Pareto analysis as appropriate.
    • Identify the sponsor and the belt for the project.
    • Estimate the saving.
    • Finalize the project charter.
    • Obtain approval for the charter.
  2. Measure

    In the measure phase, our objectives are to evaluate the current process performance and identify the potential input factors which are thought to affect the output. Key actions are listed here.

    • Characterize the process with a process map and/or value stream map, spaghetti diagram, etc.
    • Brainstorm and develop a cause and effects diagram and/or the matrix.
    • Perform measurement systems analysis (MSA).
    • Perform initial process capability study.
    • Develop data collection and sampling plan.
  3. Analyze

    In the analyze phase, the relationship between input and output factors is characterized. Important actions and tools are as given below:

    • Perform failure mode and effects analysis (FMEA).
    • Collect data and analyze with various tools such as:
      • Boxplots, dot plots, histograms
      • Scatter plots
      • Multi-vari charts
      • Other appropriate tools
    • Perform analysis using statistical tools such as:
      • Hypothesis tests: Z, t, F, Chi-square, etc.
      • Analysis of variance (ANOVA)
      • Regression: Simple or multiple
    • For lean projects, use waste analysis tools.
  4. Improve

    Based on the conclusions of the analyze phase, improvement actions are decided and implemented. Usually, optimization and fine-tuning are necessary to get the best out of the process. Key actions and tools recommended for this phase are listed below:

    • Conduct Design of Experiments.
      • Full or fractional factorial experiments
      • Response surface methods for optimization
      • Taguchi designs for robust process/product design
      • Use Kaizen or Kaizen Blitz if appropriate
      • Single minute exchange of dies (SMED)
      • Poka yoke or mistake proofing
    • Validate improvement with statistical evidence.
      • Hypothesis tests
      • Process capability evaluation
  5. Control

    Once the solution is implemented and validated, it is essential to ensure that improvement is sustainable. Actions and tools required in the control phase follow.

    • Training for transition
    • Process owners sign-off
    • Use of control charts to monitor processes to assure stability
      • Variable control charts: X-bar and range, X-bar and standard deviation, individuals and moving range
      • Attribute control charts: proportion defective, number defective, number of defects, defects per unit (DPU)
    • Control plans to address control methods, responsibilities and actions to be taken in the case of process deterioration
    • Poka yoke or mistake proofing
    • 5S, Visual Factory, Kan-ban
    • Total productive maintenance (TPM)

Cause and effects relationship between the KPOVs (‘Y's) and KPIVs (‘X's) gets clearer as the project goes through the five phases. Some of the tools used in the Six Sigma approach are listed in Table 1.2. The project leaders must ensure that the key deliverables of the project are achieved and demonstrated.

DMAIC Project Examples

Six Sigma was initially evolved for manufacturing processes. However, later the Six Sigma approach resulted in applying the tools to business processes with large gains. Some examples of the poor quality of business processes are given below.

  • Poor supplier quality and/or delivery performance can result in missed deliveries to our customers, lost man-hours due to parts not being available on time, excess inventory and customer complaints.
  • An incapable process can produce bad parts which require either rework or need to be scrapped. This is a direct loss to the company and will adversely affect quality as well as productivity. Moreover, processes with poor capabilities result in inventories as a cushion for the low predictability. Six Sigma tools such as Multi-vari (MV) charts, Anova, designed experiments, regression, can be very effective in pin-pointing causes of variation so that we can reduce it.
  • Many medium- and large-scale companies use enterprise resource planning (ERP) systems to manage their operations. This software relies heavily on the accuracy of specifications, accuracy of supply chain and manufacturing data, cycle times and robustness of change-control systems. The impact of inaccuracy on these data can result in incorrect parts, short or wrong parts, incorrect inventory, missed deliveries, etc. The financial impact of these could be significant depending on the degree of in accuracy. With financial auditors tightening their belts, the impact of incorrect inventory depletions could be as high as 2 percent of the profit. Accuracy of product specifications and inventories are typical candidates for Six Sigma projects. Lean Six Sigma tools such as mapping the process, cause and effects analysis, FMEA, regression, MV charts can be appropriate for quickly finding direction for improvement.
  • Time taken to implement engineering changes and database updating can be a major hurdle when it comes to launching new products in time. Lean tools such as value stream mapping can be used to identify non-value-added steps in the process so that we can minimize or eliminate these to reduce process time.
  • A service organization such as a call center can have either insufficient and/or untrained staff. The online support system may not provide quick and easy navigation to solve all types of customer calls. Over and above, the staff may not be empowered to independently solve customer-related issues. As a result, a customer can get irritated for having to wait long and making repeat calls to get service. Lean Six Sigma can help in reducing the waiting period.


Table 1.2 Six Sigma tools and their usage pattern


My personal experience with the service industry in India is somewhat disappointing. The manufacturing industry is relatively better positioned in terms of quality and reliability performance.

Design for Six Sigma (DFSS) Roadmaps

DFSS is used to conceive, design, optimize and certify the capability of a new product design or manufacturing process. It can also be used to improve a current manufacturing process or product design that has radically different performance requirements.

The DMAIC roadmap is not appropriate for DFSS. A more suitable roadmap of DFSS approach is

  1. Define
  2. Measure
  3. Analyze
  4. Design
  5. Verify/Validate

This roadmap is commonly referred as DMADV. Table 1.3 shows the commonly used DFSS tools.


Table 1.3 An overview of the DFSS tools


Alternate but effective DFSS roadmaps are recommended by Creveling, Stutsky and Antis in Design for Six Sigma (2003). When a company wants to develop a new technology, the recommended roadmap will constitute the following steps.

  1. Invent and Innovate
  2. Develop
  3. Optimize
  4. Verify and Validate

This is often referred to as I2DOV.

For product design and development, Creveling, Stutsky and Antis suggest the following roadmap.

  1. Concept
  2. Design
  3. Optimize
  4. Verify and Validate

This roadmap is usually referred to as CDOV.

I2DOV and CDOV roadmaps have been deployed in Cummins. These roadmaps will be discussed in more detail in Chapter 10 on Design for Six Sigma (DFSS).

DFSS Project Examples

  1. Develop new transmission to improve durability from 1,75,000 km to 300,000 km. In this case, durability is measured as B10 life (distance covered in kilometers by which time 10 percent of systems will require their first overhaul).
  2. Improve the current engine system to assure compliance with new emission regulations.
  3. Design and develop a new truck cabin for better comfort, ease of operation, and aesthetics. Comfort conditions include vibrations, noise, temperature, space, and ease of operation. This project mainly relates to the layout. Driving effort is not included in the project scope.
  4. Design and develop a cooling system for a new car model. The cooling system should have
    • Ten percent better thermal efficiency and
    • Fifty percent lower failures in warranty.
Criticism of Six Sigma

There has been a lot of criticism of Six Sigma. Many feel that the tools used in the approach have already been in existence and in reality there is nothing new in this. In short, Six Sigma is just an old wine in a new bottle. The criticism is true in a way. However, others feel that while the tools existed earlier, quantification of the metrics and direct relation to the bottom line makes it different. Another major criticism is about the high price tag attached to Six Sigma training. Occasional criticism of Six Sigma is that it results in only short-term improvement projects. This is countered by its proponents who maintain that although a project usually runs for six months, the black belts in turn take up the next project and also train others in the Six Sigma methodology. As more black belts are trained and a large number of projects are completed, the organization achieves long-term benefits (Urdhwareshe 2001).

Organizing for Six Sigma

Implementing Six Sigma requires the strong foundation of an organization that supports and encourages employees to embrace the Six Sigma philosophy. It is important that the senior management actively participates in setting up direction of the program. A Six Sigma program must be initiated by the chief executive officer with specific objectives and the top management team must be committed and supportive of the program to make it a success. The depth of Six Sigma implementation can vary greatly in companies. There are companies that consider Six Sigma as a corporate initiative. The CEO of the company is highly committed and supportive of Six Sigma implementation. Under such circumstances, people at the operating level are usually charged up and motivated to take up projects and complete these successfully. If Six Sigma implementation is announced on the insistence of a customer, the implementation is likely to be superficial. Management commitment is demonstrated by the amount of time the senior managers devote to Six Sigma. Absence of senior management from project selection, review and other meetings is a clear indicator of a lack of commitment.

Role of the Management in Six Sigma

Let us look at the roles that the management plays in a company implementing Six Sigma.

Executive Leadership

Executive leadership and the leadership team's responsibility is to

  • state the overall objectives of Six Sigma initiative and set the direction;
  • identify and communicate priority areas for focusing Six Sigma efforts;
  • benchmark other organizations and/or competitors for performance and Six Sigma implementation; and
  • allocate resources for Six Sigma implementation in terms of people, financial budgets, logistics, hardware, software, training, etc.

Key Players of a Six Sigma Program

There are some typical terms used by the Six Sigma community to address its members and processes. These terms have been used this book as well. A simple explanation of these is provided here.

The Champion

The Champion is the initiative leader for Six Sigma in an organization. Quite often, the champion is the CEO of the company or one of his/her direct reports. A champion

  • announces and initiates the Six Sigma program in the company;
  • sets and/or communicates the overall objectives of the Six Sigma program;
  • sets up targets for business units in terms of business measures such as financial savings, customer defects, delivery performance, etc.;
  • supports and provides resources for Six Sigma training;
  • monitors periodically the progress with reference to plans and targets;
  • resolves any organizational issues; and
  • sets up the steering committee structure involving all functional heads.


Sponsors are senior business managers who own the projects. They are stakeholders in the success of the project and are accountable for the outcome. They must support the belts in terms of making resources available to them, motivating and challenging them and the team members. The support from sponsors can mean budgetary approvals, team members’ time and availability, ensuring help from other departments, etc. They should report the progress and status of projects sponsored by them in top management reviews. Some companies get feedback from belts about support by sponsors.

Sponsors are responsible for

  • identifying project opportunities which link strongly to the organizational goals and objectives;
  • identifying potential black and green belts and releasing them for Six Sigma projects either full time in case of black belt projects or part time in case of green belt projects; and
  • conducting periodic project reviews to ensure that belts get the necessary support in terms of team members’ time, budgets, financial approvals, travel approvals, etc. (I have personally experienced that if the sponsors are required to present project progress, they are forced to review the same with the belts.)

They should also

  • demonstrate their commitment by taking up green belt or black belt projects;
  • recognize and reward the belt and team members on successful completion of projects;
  • share the success stories and best practices in appropriate forums; and
  • ensure a smooth transition to the process owners after the completion of projects.


Belts lead the projects. Black Belts work full time, and are the ‘epicenters’ of the Six Sigma projects. They are on the battleground of Six Sigma. They execute and demonstrate the power of Six Sigma to the business leaders. Black belts are carefully selected and are critical resources in Six Sigma implementation. Savings in black belt projects are typically around US$250,000 or above. However, norms for project savings differ considerably among companies. Black belts are trained for in-depth understanding of the Six Sigma approach and tools. Black belt training duration is usually between 3 to 4 weeks. In most cases, black and green belts undergo training and immediately start applying the tools to their project. Many organizations consider black belts as future leaders of the company and select them after critical evaluation of their potential capabilities

Green Belts work part time as projects of lesser complexity may not require full-time resource. In some organizations, green belts assist black belts in data collection, process maps, conducting capability studies, etc. Duration for green belt training is somewhat less, typically around 6 to 10 days. Savings and complexity of green belt projects can be lower than black belt projects. Green belts are usually chosen from the same functional area.

Master Black Belt (MBB) trains and coaches black and green belts. He/she is a person who has demonstrated the power of Six Sigma in 3 to 5 projects of companywide importance. MBB is usually (or must be) respected by others for his/her leadership, problem-solving skills, coaching and mentoring skills, communication with senior management. MBB must enjoy the trust of the senior management in order to succeed. In many companies, MBB is expected to track the progress of Six Sigma projects by conducting periodic project reviews and publishing status report to the sponsors and the champion. The responsibilities of the MBB are to

  • conduct training of black and green belts;
  • coach the belts for the selection and use of appropriate Six Sigma tools;
  • conduct project reviews at each phase, i.e., DMAIC;
  • suggest ideas in case the belts struggle to make progress due to lack of experience;
  • organize and conduct project closure reviews and approve or disapprove closures;
  • manage the Six Sigma database; and
  • share success stories with other MBBs in various business units. Quite often, similar projects are taken at different plant locations.

Financial Controller

Financial Controller validates savings. Six Sigma projects should have significant financial benefits. Savings claimed by the belts are reviewed and endorsed by the controller, who also reviews the actual savings at the closure of projects. The role of the head of finance is important in Six Sigma implementation. Each Six Sigma project requires the estimation of financial benefits. These benefits are usually estimated by the belts and their sponsors and then approved by the financial controller, who is appointed by the head of finance. This is a very important role as financial benefits will have a positive impact on the bottom line of the company.

HR Functional Head

The role of the HR functional head is important in ensuring that the performance management system of the company gives due importance to Six Sigma. Companies like GE and Cummins consider involvement in Six Sigma implementation as belt and/or sponsor a mandatory requirement for promotions and performance awards.

Quality Leader

Quality Leader of the company is usually an anchor for the Six Sigma initiative. If the management representative (MR) for ISO 9000 certified system is different, he/she would also need to support the belts. As a quality leader and MR at Cummins India, I was a member of the steering committee and project closure reviews. I played a significant role in project selection, identifying potential black belts, green belts, providing organizational support, data collection, system documentation, etc. I also sponsored many projects and led projects related to improving customer satisfaction. Other functional heads must demonstrate their commitment by identifying projects to improve the overall business performance, by leading/sponsoring projects, supporting the belts, recognizing belts and team members, ensuring smooth transition to process owners after completion.

Process Owners

Process Owners are responsible for running a process in the organization. For example, a production engineer can be a process owner for production of parts, productivity, etc.

  • Process owners usually support Six Sigma belts as team members to provide data collection, conduct experiments, participate in FMEA and process maps, etc.
  • Involvement of the process owners is essential for the success of Six Sigma projects. Lack of their involvement can lead to unacceptability of solutions.
  • Process owners must accept and approve the closure of projects as they have to run the process regularly. Their role is especially important for training the persons responsible for operating the machinery or other equipment in the process.

The Six Sigma Steering Committee

A formal way of driving Six Sigma is through the steering committee of the senior leadership team: A typical steering committee may look like the diagram in Figure 1.7. The role of the CEO is to provide the big picture and strategic objectives to the management team. The senior management of the company, especially the CEO and the quality leader, have key responsibilities in creating faith in the program. MBBs usually review projects periodically and report the status to the committee. Typical functions of the steering committee are listed below:



Figure 1.7 Six Sigma steering committee


  • Monitoring the overall progress of the Six Sigma program
  • Ensuring that Six Sigma projects align well with strategic goals of the company
  • Deciding on implementation partner
  • Selection of projects and belts
  • Providing adequate resources for the program
  • Sponsoring black and green belt projects
  • Working on some of the projects as belts in the first phase
    • This helps in giving a message about seriousness of the effort
    • It also helps in creating faith and understanding the power of the Six Sigma approach and tools
  • Evaluating progress and financial benefits
  • Conducting project closure reviews
  • Recognizing belts and teams by occasionally giving them award/prize in the form of certificates, mementos, t-shirts, or pens.

One of the major benefits of an effective Six Sigma program is the development of future leadership. Black belts who demonstrate leadership skills in project implementation usually get exposed to the important processes in the company. They also start commanding a certain degree of respect while demonstrating their competence as project leaders. This is fundamental for the development of future leaders. Many companies that have implemented Six Sigma now require that only those who have led Six Sigma projects qualify for key positions.

Black and green belts may face organizational challenges in making their project successful. All the senior management team members, i.e., the champion, sponsor, MBB, must celebrate the success of Six Sigma at various levels. They should also share success stories across the company. An online database of Six Sigma projects is an excellent way to share projects and generate project ideas.

Typical areas which require senior management's attention are project selection, sponsors’ reviews, selection of belts, providing support in terms of time from team members. The master black belt (MBB) or Six Sigma coordinator in the company can track the timeliness of project reviews, status of projects and other action items so that any concerns are immediately surfaced out and can be resolved.

The role of other functional heads is also important for the success of Six Sigma. For example, sometimes financial approvals of project savings can take considerable time or the departmental managers may not relieve the belt for his/her new role. The MBB and the champion must together resolve such issues.

Strategic Selection of Six Sigma Projects and Belts

The senior management sometimes feels that the current quality processes are not working well to achieve the overall strategic plan. Hence, Six Sigma tools and concepts are used to enhance the existing quality processes and supplement the skills of the key people, thereby making breakthrough improvements. Six Sigma projects are identified considering the

  • strategic direction of the company;
  • the impact on the bottom line; or
  • the impact on customer satisfaction.

One of the essential elements of Six Sigma is strong linkage of each project to the company business and financials. At GE Capital, for example, mortgage customers had to use voicemails or call again in about 24 percent of calls because employees were not available (Welch 2001). Their Six Sigma team found that one of the branches had almost 100 percent calls answered. They benchmarked the process, system, layout and staffing to improve other branches. As a result, the percentage of calls answered the first time rose from 76 to 99.9. At GE Plastics, a Six Sigma team improved the plastic purity from 3.8 to 5.7 sigma level to capture business from Sony. These examples illustrate how projects are linked strongly to customers and businesses. The projects that have a significant impact usually require project leaders with high degree of competence. Black belts are carefully selected to execute the project that is critical for success. The project leaders go through in-depth training in the Six Sigma approach and tools and work full time on the project that is expected to be completed in about 6 months. Typical savings expected from a black belt project may be of the order of US$250,000 (INR 10,000,000). Black belts in many companies such as GE, Motorola, and Cummins have a tenure of two years. During these two years, they are expected to take up and complete five to ten projects that are strategically important for the company. After two years, they usually take up a leadership position in the business.

Jack Welch has mentioned clearly in Straight from the Gut that he made all the efforts to ensure that the best people are selected and trained as black belt (Welch 2001). In the initial phases, his business unit leaders (BUL) considered Six Sigma as one of ‘those’ initiatives which will ‘live’ for a short while. In the initial stages of Six Sigma, only 25 to 50 percent of the black belts were best performers. When Jack Welch allocated the employee stock options sufficient only for the black belts, then these BULs realized how serious their leader was in executing Six Sigma. Still it took GE three years to ensure that almost all black belts were high potential managers. Involving the best people in Six Sigma is essential for its success. It is obvious that these best performers must get the most important projects in order to make sustainable breakthrough improvements in the organization.

The project-based approach requires lesser resources for training that can be customized. Some of the potential failure modes of this approach are that trained engineers tend to get isolated and there may be communication barrier due to lack of common language. Most companies implementing Six Sigma today use the project-based approach to Six Sigma.

The Saga of Continuous Improvement

Bill Smith and Motorola get credit for inventing Six Sigma. This is fair and appropriate. However, we must remember that most of the Six Sigma tools existed even before Six Sigma was born. Six Sigma is a resultant or culmination of contribution of many great quality gurus in the ever-unfinished journey towards organizational excellence. Principles and tools of Six Sigma are not new. It would be appropriate to take a look at the champions of the progress in this saga of continuous improvement.

Abraham de Moivre first introduced normal distribution in 1733 which is one of the foundation stones of the Six Sigma philosophy. The very Six Sigma metric is defined using normal distribution. De Moivre used the normal distribution to approximate the distribution of the number of heads resulting from many tosses of a fair coin. This was the first version of Central Limit Theorem.

Gauss became associated with this set of distributions when he analyzed astronomical data using normal distribution and defined the equation of its probability density function. Normal distribution is, therefore, often called Gaussian distribution.

Sir Ronald Aylmer Fisher (1890–1962), an English statistician, made very important contributions in the design and analysis of experiments during the 1920s. Fisher was a Fellow of Royal Society. He worked in Rothamsted Agricultural Experiment Station where he made many contributions to the design and analysis of experiments. Fisher created the theory of experimental design. Design of experiments (DOE) is a method by which many variables controlling a process are varied at the same time. This was a major advance over the approach of varying only one factor at a time (OFAT) in an experiment. DOE is much more efficient compared to OFAT. Fisher published a number of important texts; the noted ones being Statistical Methods for Research Workers (1925), The Design of Experiments (1935) and Statistical Tables (1947).

Many of the Six Sigma tools can easily be traced back to Fisher's contributions.

Dr Walter A. Shewhart is known as ‘Father of Statistical Quality Control’. Dr Shewhart developed the theory of control charts in 1920s. Bell Telephone's engineers had been working to improve the reliability of their transmission systems. There was a business need to reduce the frequency of failures and repairs. Dr Shewhart joined the Western Electric Company Inspection Engineering Department at the Hawthorne Works in 1918. Shewhart is known for his outstanding contribution to the theory of Statistical Process Control (SPC).

His book The Economic Control of Quality of Manufactured Product was published in 1931. Shewhart's charts became more popular in 1940s at the time of Second World War. Those who used them realized substantial gains in quality and productivity. Interestingly, control charts developed by Shewhart are still used in more or less the same form. Shewhart is also known for his contribution in Plan-Do-Check-Act (P-D-C-A) cycle (See Figure 1.8) of continuous improvement. The similarity of the Six Sigma D-M-A-I-C roadmap with P-D-C-A cycle is obviously not a coincidence.



Figure 1.8 P-D-C-A cycle


Dr W. Edwards Deming's teachings of his management philosophy in Japan after 1950 created a total transformation in Japanese business resulting in what is known today as the ‘Japanese Industrial Miracle’. In recognition of his achievements in providing the theory and methods to improve the quality and dependability of manufactured products, Dr Deming was honoured by the Japanese Emperor with the Second Order Medal of the Sacred Treasure. Deming's 14 points for management keep guiding us even today. His book Out of the Crisis is considered an important contribution to the progress of quality management.

Dr Joseph Juran defined quality as fitness for use. Like Dr Deming, he too was invited to Japan in 1954 by the Union of Japanese Scientists and Engineers (JUSE). Juran emphasized that ‘quality does not happen by accident, it must be planned’. Juran advocated a ‘Trilogy’ for managing quality.

  1. Quality Planning
  2. Quality Improvement
  3. Quality Control

We can visualize a similarity between the Trilogy and the Six Sigma roadmap.

Juran recommended improvements by taking on prioritized projects. He suggested the use of Pareto analysis for prioritization. We can easily find roots of the project-based approach and Six Sigma roadmap in Juran's philosophy.

Dr Taguchi, in contrast to Western definitions, defined quality as ‘loss imparted by the product to society from the time the product is shipped’. This loss includes not only the loss to the company, but also costs to the customer through poor product performance and reliability, leading to further losses to the manufacturer as his market share falls.

The classical design of experiments methodology founded by R. A. Fisher was primarily aimed at optimizing mean response. Taguchi added philosophy and methodology of reducing variation while optimizing the mean. He called this approach as robust design. In his famous Quality Engineering Methodology (2005), Taguchi emphasized optimization of products and process prior to manufacture, rather than emphasizing the achievement of quality through inspection. His approach of parameter and tolerance design provides an efficient technique to design robust products.

Figure 1.9 shows the parabolic loss function. With this concept, loss will occur even when the product is within the permissible specifications, but is minimal when the product is on target. If the quality characteristic or response is required to be maximized (e.g., strength of concrete), or minimized (e.g., call length in a call center), then the loss function becomes half-parabola. The loss function may be used to evaluate design decisions considering the financial impact. According to Taguchi, the mathematical equation for quality loss function is given by




Figure 1.9 Taguchi's loss function


where L is loss, k is a constant and (Y – T) is the distance of the characteristic from the target. Thus, increase in loss is proportional to the square of the distance from the target. Taguchi's contributions later became the foundation of design for Six Sigma (DFSS).

Kaoru Ishikawa made significant advancements in the quality improvement process with his cause and effects diagram. This is also known as fishbone or the Ishikawa diagram. With the use of this diagram, the user can see all possible causes of a problem. Ishikawa showed the importance of statistical quality tools: Pareto chart, checksheets, process capability diagrams, control chart, stratification, histogram, scatter diagram, and flow chart in solving problems and for continuous improvement. He emphasizes systematic implementation of total quality control (TQC) across the company in conjunction with personnel management, cost control, profit control, production and delivery (Ishikawa 2006). Additionally, Ishikawa explored the concept of quality circles. Many of Ishikawa's contributions can be clearly seen in the Six Sigma approach and tools.

Dr Armand V. Feigenbaum is known for his contribution to total quality control (TQC). The first edition of his book Total Quality Control was completed whilst he was still a doctoral student at MIT. His work was discovered by the Japanese in the 1950s at about the same time as Juran visited Japan. Feigenbaum worked in the General Electric Company as the Head of Quality where he had extensive contacts with such companies as Hitachi and Toshiba. Like Ishikawa, Feigenbaum advocated systematic total approach to quality, requiring the involvement of all functions in the quality process, not just manufacturing. The idea was to build in quality at an early stage, rather than inspecting and controlling quality later.

Dr Feigenbaum helped many companies, including the Cummins Engine Company, to establish quality management system based on his total quality system (TQS). I was responsible for driving TQS implementation at Cummins India Limited during the period 1995 to 1998 and have personally experienced the profoundness of the TQS at Cummins.

Philip Crosby's name is perhaps best known in relation to the concepts of ‘Do It Right First Time’ and ‘Zero Defects’ (1980). He considers traditional quality control, acceptable quality limits and waivers of sub-standard products to represent failure rather than assurance of success. Crosby, therefore, defines quality as conformance to the requirements which the company itself has established for its products based directly on its customers’ needs. He believed that since most companies have organizations and systems that allow (and even encourage) deviation from what is really required, manufacturing companies spend around 20 percent of revenues doing things wrong and doing them over again. According to Crosby this can be 35 percent of operating expenses for service companies.

In the Crosby approach the quality improvement message is spread by creating a core of quality specialists within the company. There is strong emphasis on the top-down approach, since he believes, without reservation, that the senior management is entirely responsible for quality. Six Sigma actually aims at less than 3.4 defects per million. This is nearly zero defect, thanks to the vision of Philip Crosby. The quality specialists can be compared with the black and green belts.

Shigeo Shingo is a somewhat lesser known quality guru in the West. Shingo has helped revolutionize the way we manufacture goods. His improvement principles vastly reduce the cost of manufacturing, substantially reduce defects and improve quality, and give us a strategy for continuous improvement through the creative involvement of all employees. One of Shingo's important contributions was his development of poka-yoke and source inspection system. The philosophy of ‘poka yoke’ is to prevent mistakes from being made, i.e., identify errors before they become defects. Thus, defects are detected and corrected at source, rather than at a later stage. Shingo emphasized the practical achievement of zero defects by good engineering and process investigation. Shingo also made significant contributions in quicker set-up changes (Liker 2004). He was not a Toyota employee but worked closely with Toyota. As a passionate industrial engineer, he analyzed every minute step in the set-up changes for large stamping presses at Toyota. With his efforts and innovation, the set-up times were reduced to few minutes from few hours. This approach is often called ‘Single (Digit) Minute Exchange of Dies’ (SMED). Shingo's Poka Yoke and SMED approach are critically important in the improve and control phases of Lean Six Sigma.

A Summary of the Contributions by Quality Gurus

Table 1.4 summarizes the contributions made by some of the quality gurus.


Table 1.4 Contributions by quality gurus

S.no. Contribution Quality expert
Normal distribution Abraham de Moivre
Design of experiments, analysis of variance, statistical tables Sir Ronald Fisher
Statistical process control and control charts Dr Walter Shewhart
Fourteen quality management principles, management responsibility Dr Deming
Quality planning, Juran trilogy, project-based approach to improvement, prioritization using Pareto analysis Dr J. M. Juran
Orthogonal arrays, linear graphs, signal to noise ratio, robust design, loss function Dr Genichi Taguchi
Zero quality control, source inspection, mistake-proofing (Poka Yoke), SMED Shigeo Shingo
Do it right first time, zero defect, cost of rework and poor quality in each process Philip Crosby
Cause and effects diagrams, QC tools for continuous improvement Kaoru Ishikawa

The Six Sigma approach evolved at Motorola and was later adapted by many other companies such as GE, Allied Signal, Cummins, and so on. Bill Smith created the idea and roadmap of Six Sigma.

Six Sigma is a project-based approach. It aims at reducing variation to the extent that the defect level is extremely low. The projects must strongly link with the company's strategic objectives and the benefits should be quantified in financial units. The project leaders called belts are carefully selected.

Process Sigma roadmap is Define-Measure-Improve-Analyze-Control. DFSS roadmap is Define-Measure-Analyze-Design/Develop-Verify/Validate. Intensive training to the belts on the approach and tools is an integral part of implementing Six Sigma. The tools include many advanced statistical methods that accelerate the process of root-cause investigation.

Most of the tools deployed in Six Sigma were in use much before the term came into existence. However, the use of many of these was limited to expert statisticians only. Six Sigma training makes these complex tools available to the belts who are not statisticians. Integrating these tools to improve processes to gain financial benefits is what differentiates Six Sigma from other TQM approaches.


Bondre, Shobha (2006). Mumbaicha Annadata. (In Marathi language.) Pune: Rajhans Publishers.

Chadwick, Gail (2000). Remembering Bill Smith, Father of Six Sigma. Published by www.isixsigma.com

Creveling, C. M., J. L. Slutsky, and D. Antis, Jr. (2003). Design for Six Sigma in Technology and Product Development. Upper Saddle River, NJ: Pearson.

Crosby, Philip (1980). Quality Is Free. New York, NY: Penguin Books.

George, Michael L. (2002), Lean Six Sigma: Combining Six Sigma Quality with Speed. New Delhi: Tata McGraw Hill.

Hahn, Gerald J., Necip Doganaksoy, and Roger Hoerl (2000). ‘The Evolution of Six Sigma’. Quality Engineering. Vol. 12, Issue 3. pp. 317–326.

Harry, Michael (2000). Six Sigma: The Breakthrough Management Strategy Revolutionizing the World's Top Corporations. New York, NY: Currency/Doubleday.

Ishikawa, Karou (2006). Introduction to Quality Control. Chennai: Productivity Press.

Juran, J. M. and Frank M. Gryna (1999). Juran's Quality Control Handbook. New York: McGraw Hill.

Liker, Jeffrey K. (2004). The Toyota Way. New York, NY: McGraw Hill.

Mader, Douglas P. (2008). ‘Lean Six Sigma's Evolution’, Quality Progress. January 2008.

McCarty, Tom (2004). ‘Six Sigma® at Motorola’. European CEO. September–October 2004. Leadership Edition. www.motorola.com/mot/doc/1/1736_MotDoc.pdf. Accessed on 26 Nov 2009.

Pyzdek, Thomas (2003). The Six Sigma Handbook: A Complete Guide for Green Belts, Black Belts and Managers at All Levels. New York, NY: McGraw Hill.

Taguchi, Genichi (2005). Taguchi's Quality Handbook. Dublin: Mentor Books.

Urdhwareshe, Hemant (2000). ‘The Six Sigma Approach’. www.symphonytech.com/articles/sixsigma.htm. Last accessed on 26 November 2009.

Welch, Jack (2001). Straight from the Gut. New York: Warner Books. “http://www.qualitygurus.com/gurus” accessed on 27 November 2009.