6 Sigma

1. 1
Six Sigma
Introduction
Six Sigma (6σ) is a set of techniques and tools for process improvement. It was introduced by
engineers Bill Smith & Mikel J Harry while working at Motorola in 1986. Jack Welch made it
central to his business strategy at General Electric in 1995.
It seeks to improve the quality of the output of a process by identifying and removing the causes
of defects and minimizing variability in manufacturing and business processes. It uses a set of
quality management methods, mainly empirical, statistical methods, and creates a special
infrastructure of people within the organization who are experts in these methods. Each Six Sigma
project carried out within an organization follows a defined sequence of steps and has specific
value targets, for example: reduce process cycle time, reduce pollution, reduce costs, increase
customer satisfaction, and increase profits.
The term Six Sigma (capitalized because it was written that way when registered as a Motorola
trademark on December 28, 1993) originated from terminology associated with statistical
modeling of manufacturing processes. The maturity of a manufacturing process can be described
by a sigma rating indicating its yield or the percentage of defect-free products it creates. A six-
sigma process is one in which 99.99966% of all opportunities to produce some feature of a part
are statistically expected to be free of defects (3.4 defective features per million opportunities).
Motorola set a goal of "six sigma" for all of its manufacturing operations, and this goal became a
by-word for the management and engineering practices used to achieve it.
What is Six Sigma
Six Sigma is a defined and disciplined business Methodology to increase customer
satisfaction and profitability by streamlining operations, improving quality and
eliminating defects in every organization wide process.
A Business Strategy: Using Six Sigma Methodology, a business can strategize its plan
of action and drive revenue increase, cost reduction and process improvements in all parts of the
organization.
A Vision: Six Sigma Methodology helps the Senior Management create a vision to provide
defect free, positive environment to the organization.
A Benchmark: Six Sigma Methodology helps in improving process metrics. Once the
improved process metrics achieve stability; we can use Six Sigma methodology again to improve
the newly stabilized process metrics. For example: The Cycle Time of Pizza Delivery is
improved from 60 minutes to 45 minutes in a Pizza Delivery process by using Six Sigma
methodology. Once the Pizza Delivery process stabilizes at 45 minutes, we could carry out

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another Six Sigma project to improve its cycle time from 45 minutes to 30 minutes. Thus, it is a
benchmark.
A Goal: Using Six Sigma methodology, organizations can keep a stringent goal for themselves
and work towards achieving them during the course of the year. Right use of the methodology
often leads these organizations to achieve these goals.
A Statistical Measure: Six Sigma is a data driven methodology. Statistical Analysis is used to
identify root-causes of the problem. Additionally, Six Sigma methodology calculates the process
performance using its own unit known as Sigma unit.
A Robust Methodology: Six Sigma is the only
methodology available in the market today
which is a documented methodology for problem solving. If used in the right manner,Six Sigma
improvements are bullet-proof, and they give high yielding returns
Why Six sigma
Help Your Organization Eliminate Errors
From an organization’s perspective, acquiring a Six Sigma certification enables an individual to
become crucial to an organization’s ability to identify and eliminate repeatable process
errors. With a Six Sigma certification, you would be able to transform and enable an organization
to increase revenue by identifying and eliminating errors that would otherwise have brought poor
customer satisfaction and losses to the business. Certified Six Sigma professionals can help reduce
invoicing errors, customer complaints, complaint resolution time, spending, schedule delays, and
cost overruns.
For example: in 1998, GE attributed their $350 million in savings to the Six Sigma process, while
Motorola attributed their highest savings of $17 billion in 2005 to Six Sigma. GE’s savings rose
to more than $1 billion later that decade.
Improve Business Processes and Sustain Quality Improvement
Once you attain the Six Sigma certification, you’ll be able to prove you have the knowledge to identify the
characteristics of an organization’s manufacturing and business processes and be able to measure, analyze,
control, and improve them. You will also have the ability to conduct a complete review of current practices
and gain a very clear understanding of their impact on quality performance.
Applicability Across Industries
What is the value of a Six Sigma certification? As an industry-agnostic methodology, Six Sigma
techniques are applied in aerospace, electronics, telecom, banking and financial services, IT, HR,
marketing, and many more industries.

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Getting a Six Sigma certification can lead to better job opportunities and improved salary—even
though it’s not easy to attain. One of the reasons Six Sigma certified professionals get so much
respect is that the exams are not easy to pass—and executives and hiring managers at major
companies are well aware.
Ensure Compliance
With the stringent quality standards of Six Sigma, manufacturing and process errors are reduced to
insignificant figures. This has meant that a number of vendors, procurers, and oversight organizations apply
Six Sigma standards when evaluating products or accounts. As a certified Six Sigma professional, you will
be able to help your organization comply with international standards, as well as maintain profitable
contracts.
Helps Nurture Managerial And Leadership Ability
Six Sigma training also prepares you for leadership roles, with the techniques and knowhow to cut
costs, increase revenue, and ways to improve the efficiency of the business process. Those who
achieve Six Sigma Black Belt are not only educated on the methodologies of Six Sigma, they are
also prepared to become a change agent within their organization, leading efforts to improve
processes and the quality of products and services delivered to customers.
Once you complete your Six Sigma course and obtain your certification, you will have a clear
understanding of measuring and quantifying financial benefits from executing any Six Sigma
project. Because financial management and risk assessment are highly desirable skills for middle
and top-level management, certified Six Sigma professionals stand a very good chance of rising to
senior managerial positions.
Excellent Salary
According to a survey carried out by indeed.com, the salary for Six Sigma certified individuals routinely
break into the $100,000+ pay bracket, and are among the highest-paid professionals globally.
Gain Hands-On Experience in Quality Management
Unlike a few other certifications, the Six Sigma certification process includes hands-on work on
industry projects and experience with implementation of theoretical principles to real-life
scenarios. As a certified Six Sigma professional, you will gain valuable experience even before
you enter the workforce.
Ready to get started on the path to Six Sigma Master Black Belt? Simplilearn's Lean Six
Sigma master's program is taught by Green and Black Belt certified professionals with more than
ten years of industry experience in implementing Quality Management and will help you become
a Lean Six Sigma champion.

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Principles:
There are some principles in Six Sigma. These have been depicted below;
1) Focus on the customer.
2) Identify and understand how the work gets done. (the value system)
3) Manage, improve and smooth the process flow.
4) Remove non-value-added steps and waste.
5) Manage by fact and reduce variation.
6) Involve and equip the people in the process.
7) Undertake improvement activity in a systematic way.
Historical overview of Six Sigma
The roots of Six Sigma as a measurement standard can be traced back to Carl Friedrich Gauss
(1777-1855) who introduced the concept of the normal curve. Six Sigma as a measurement
standard in product variation can be traced back to the 1920’s when Walter Shewhart showed that
three sigmas from the mean is the point where a process requires correction. Many measurement
standards (Cpk, Zero Defects, etc.) later came on the scene but credit for coining the term “Six
Sigma” goes to a Motorola engineer named Bill Smith. (Incidentally, “Six Sigma” is a federally
registered trademark of Motorola).
In the early and mid-1980s with Chairman Bob Galvin at the helm, Motorola engineers decided
that the traditional quality levels — measuring defects in thousands of opportunities – didn’t
provide enough granularity. Instead, they wanted to measure the defects per million opportunities.
Motorola developed this new standard and created the methodology and needed cultural change
associated with it. Six Sigma helped Motorola realize powerful bottom-line results in their
organization – in fact, they documented more than $16 Billion in savings as a result of our Six
Sigma efforts.
Since then, tens of thousands of companies around the world have adopted Six Sigma as a way of
doing business. This is a direct result of many of America’s leaders openly praising the benefits of
Six Sigma. Leaders such as Larry Bossidy of Allied Signal (now Honeywell), and Jack Welch of
General Electric Company. Rumor has it that Larry and Jack were playing golf one day and Jack
bet Larry that he could implement Six Sigma faster and with greater results at GE than Larry did
at Allied Signal. The results speak for themselves.
Six Sigma has evolved over time. It’s more than just a quality system like TQM or ISO. It’s a way
of doing business. As Geoff Tennant describes in his book Six Sigma: SPC and TQM in
Manufacturing and Services: “Six Sigma is many things, and it would perhaps be easier to list all
the things that Six Sigma quality is not. Six Sigma be: a vision; a philosophy; a symbol; a metric;
a goal; a methodology.” We couldn’t agree more.

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How does Six Sigma work?
Identify Business Problem
Identify Business Problem At the beginning of a Six Sigma project, the Business Problem is
defined. Questions such as What, When, where are addressed in a problem statement. Magnitude
and Consequence of the problem is also discussed. Project Scope is identified.
Trivial Many Causes: These are all the possible causes of the given problem. They may cause
impact to the problem.
Identify Business Solution These statistical solutions are then converted to implementable
practical solutions. Implementation of these business solutions is carried out in the process.
Improvements are observed and sustained.
Identify Statistical Problem
Identify Statistical Problem Root causes for the business problems are identified. Those root causes
are converted into statistical problems using Hypothesis testing methods.
Vital Few Causes: These are the few critical causes which cause maximum impact over the
problem.
Identify Statistical Solution
Identification of only 3-4 vital root causes using statistical analysis is achieved. These root causes
are vital because they have maximum impact on the problem. Any given problem follows a Pareto
principle which states that 80% of the problems are caused due to 20% of the root-causes. Solutions
to these root causes are studied and an optimal value for each solution is identified.
Difference between related concepts
Lean management and Six Sigma are two concepts which share similar methodologies and tools.
Both programs are Japanese influenced, but they are two different programs. Lean management is
focused on eliminating waste and ensuring efficiency while Six Sigma's focus is on eliminating
defects and reducing variability.
Methodologies
Six Sigma projects follow two project methodologies inspired by Deming's Plan-Do-Check-Act
Cycle. These methodologies, composed of five phases each, bear the acronyms DMAIC and
DMADV.

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DMAIC
The five steps of DMAIC
Main article: DMAIC
The DMAIC project methodology has five phases:
• Define the system, the voice of the customer and their requirements, and the project goals,
specifically.
• Measure key aspects of the current process and collect relevant data; calculate the 'as-is'
Process Capability.
• Analyze the data to investigate and verify cause-and-effect relationships. Determine what
the relationships are, and attempt to ensure that all factors have been considered. Seek out
root cause of the defect under investigation.
• Improve or optimize the current process based upon data analysis using techniques such as
design of experiments, poka yoke or mistake proofing, and standard work to create a new,
future state process. Set up pilot runs to establish process capability.
• Control the future state process to ensure that any deviations from the target are corrected
before they result in defects. Implement control systems such as statistical process control,
production boards, visual workplaces, and continuously monitor the process. This process
is repeated until the desired quality level is obtained.
Some organizations add a Recognize step at the beginning, which is to recognize the right problem
to work on, thus yielding an RDMAIC methodology.[11]
DMADV or DFSS
The five steps of DMADV
Main article: DFSS
The DMADV project methodology, known as DFSS ("Design for Six Sigma"),features five
phases:
• Define design goals that are consistent with customer demands and the enterprise strategy.

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• Measure and identify CTQs (characteristics that are Critical to Quality), measure product
capabilities, production process capability, and measure risks.
• Analyze to develop and design alternatives
• Design an improved alternative, best suited per analysis in the previous step
• Verify the design, set up pilot runs, implement the production process and hand it over to
the process owner(s).
Quality management tools and methods
Within the individual phases of a DMAIC or DMADV project, Six Sigma utilizes many
established quality-management tools that are also used outside Six Sigma. The following table
shows an overview of the main methods used. AS
• 5 Whys
• Statistical and fitting tools
o Analysis of variance
o General linear model
o ANOVA Gauge R&R
o Regression analysis
o Correlation
o Scatter diagram
o Chi-squared test
• Axiomatic design
• Business Process Mapping/Check sheet
• Cause & effects diagram (also known as fishbone or Ishikawa diagram)
• Control chart/Control plan (also known as a swimlane map)/Run charts
• Cost-benefit analysis
• CTQ tree
• Design of experiments/Stratification
• Histograms/Pareto analysis/Pareto chart
• Pick chart/Process capability/Rolled throughput yield
• Quality Function Deployment (QFD)
• Quantitative marketing research through use of Enterprise Feedback Management (EFM)
systems
• Root cause analysis
• SIPOC analysis (Suppliers, Inputs, Process, Outputs, Customers)
• COPIS analysis (Customer centric version/perspective of SIPOC)
• Taguchi methods/Taguchi Loss Function
• Value stream mapping

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Software and Application
Main article: List of Six Sigma software packages
Main article: List of Six Sigma companies
Six Sigma mostly finds application in large organizations. An important factor in the spread of Six
Sigma was GE's 1998 announcement of $350 million in savings thanks to Six Sigma, a figure that
later grew to more than $1 billion. According to industry consultants like Thomas Pyzdek and John
Kullmann, companies with fewer than 500 employees are less suited to Six Sigma implementation
or need to adapt the standard approach to make it work for them. Six Sigma however contains a
large number of tools and techniques that work well in small to mid-size organizations. The fact
that an organization is not big enough to be able to afford Black Belts does not diminish its abilities
to make improvements using this set of tools and techniques. The infrastructure described as
necessary to support Six Sigma is a result of the size of the organization rather than a requirement
of Six Sigma itself.
Although the scope of Six Sigma differs depending on where it is implemented, it can successfully
deliver its benefits to different applications.
Manufacturing
After its first application at Motorola in the late 1980s, other internationally recognized firms
currently recorded high number of savings after applying Six Sigma. Examples of these are
Johnson and Johnson, with $600 million of reported savings, Texas Instruments, which saved over
$500 million as well as Telefonica de Espana, which reported $30 million euros of revenue in the
first 10 months. On top of this, other organizations like Sony and Boeing achieved large
percentages in waste reduction.
Engineering and Construction
Although companies have considered common quality control and process improvement
strategies, there’s still a need for more reasonable and effective methods as all the desired standards
and client satisfaction have not always been reached. There is still a need for an essential analysis
that can control the factors affecting concrete cracks and slippage between concrete and steel. After
conducting a case study on Tinjin Xianyi Construction Technology Co, Ltd., it was found that
construction time and construction waste were reduced by 26.2% and 67% accordingly after
adopting Six Sigma. Similarly, Six Sigma implementation was studied at one of the largest
engineering and construction companies in the world: Bechtel Corporation, where after an initial
investment of $30 million in a Six Sigma program that included identifying and preventing rework
and defects, over $200 million were saved.
Finance
Six Sigma has played an important role by improving accuracy of allocation of cash to reduce
bank charges, automatic payments, improving accuracy of reporting, reducing documentary credits

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defects, reducing check collection defects, and reducing variation in collector performance. Two
of the financial institutions that have reported considerable improvements in their operations are
Bank of America and American Express. By 2004 Bank of America increased customer
satisfaction by 10.4% and decreased customer issues by 24% by applying Six Sigma tools in their
streamline operations. Similarly, American Express successfully eliminated non-received renewal
credit cards and improved their overall processes by applying Six Sigma principles. This strategy
is also currently being applied by other financial institutions like GE Capital Corp., JP Morgan
Chase, and Sun Trust Banks, with customer satisfaction being their main objective.
Supply Chain
In this field, it important to ensure that products are delivered to clients at the right time while
preserving high-quality standards from the beginning to the end of the supply chain. By changing
the schematic diagram for the supply chain, Six Sigma can ensure quality control on products
(defect free) and guarantee delivery deadlines, which are the two major issues involved in the
supply chain.
Healthcare
This is a sector that has been highly matched with this doctrine for many years because of the
nature of zero tolerance for mistakes and potential for reducing medical errors involved in
healthcare. The goal of Six Sigma in healthcare is broad and includes reducing the inventory of
equipment that brings extra costs, altering the process of healthcare delivery to make more efficient
and refining reimbursements. A study at the University of Texas MD Anderson Cancer Center,
which recorded an increase in examinations with no additional machines of 45% and reduction in
patience preparation time of 40 minutes; from 45 minutes to 5 minutes in multiple cases.
Six Sigma Roles and Responsibilities
Six Sigma roles are primarily divided into two segments:
1. Initiative Leadership
2. Project Leadership
Apart from the above two segments, the overall Six Sigma methodology require the following
roles:
1. Six Sigma Deployment Leader
2. Six Sigma Champion
3. Six Sigma Master Black Belt (MBB)
4. Six Sigma Black Belt (BB)
5. Six Sigma Green Belt (GB)
6. Six Sigma Yellow Belt (YB)

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Let’s look at how Six Sigma roles are bifurcated into the required segments:
Six Sigma Project Roles
SIX SIGMA DEPLOYMENT LEADERS:
As a group, business leaders must own and drive Six Sigma by doing the following:
• Establish business objectives and the role of Six Sigma to achieve those goals.
• Create an environment which enables success including goals, measures, coaching, and
communication, among others.
• Actively participate in Six Sigma activities and projects.
Success of the effort is very highly correlated to the interest and time invested by business leaders.
Deliverables of a Six Sigma Deployment Leader:
• Six sigma strategy and roll-out plan for the overall organization
• Hire team of Master Black Belt, Black Belts, among others
• Work with MBB to identify organization vision and mission
• Provide a goal for the organization to drive Six Sigma at all levels
Benefits of being a Six Sigma Deployment Leader for Organization and for self-career:
• Six Sigma Deployment Leader helps the organization to develop the Six Sigma culture and
helps nurture a culture of continuous process improvement.
• Driving Six Sigma in the organization allows the deployment leader to run the company to
its full potential, thus, leveraging him/her the additional budget for taking more initiatives.
SIX SIGMA CHAMPIONS:
Project Champions (Sponsors) are the managers of the business, function, or value stream which
has been identified as high priority for a Six Sigma team. They play a pivotal role in that they
own the processes of the business and, therefore, must ensure process improvements are captured
and sustained.

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They typically also manage Six Sigma Green Belts (GB’s) and must understand the challenges
faced by GB associates (for example, removing roadblocks). They also must work with BB’s and
MBB’s to ensure that their business area has developed, and is implementing, a long-term vision
of a Six Sigma operating environment across the entire operative base.
Some more details and associated deliverables on the role of Six Sigma Champion
(Sponsor):
• Training: Sponsors must participate in available Six Sigma trainings.
• Support: Provide visible support for Six Sigma MBB, BB and GB’s and provide access to
resources needed to conduct the project.
• Scope: Set very clear scope for all Six Sigma projects. Ensure that the project is clearly
defined, has a scope which can be managed within 4-6 months, and which has high
likelihood of success. Watch the project as it progresses to ensure that the scope stays
strictly within the bounds originally set.
• Expectations: Set high expectations on the value of the results. Ensure the goals are not
sub-optimized. The Six Sigma process has proven in many cases to deliver value far
beyond initial estimates. Less-than-aggressive goals will yield less-than-aggressive results.
• Facts: Challenge Experts on their Knowledge of facts and the basis of their conclusions.
• Involvement: Sponsors are expected to interact with project teams on a regular basis to
participate in problem solving, make decisions, and allocate resources. Plan to spend at
least 2 hours every other week with the project team.
• Hand-over: Sponsors will be responsible for ensuring that the business takes ownership
of the implementation and delivers the value indicated in the Control phase. This requires
a specific individual who will own the delivery of the project metrics.
• Results: Sponsors, as well as 6sigma mentors and business controllers, are responsible for
ensuring that project results hit the bottom line of the organization.
Benefits of being a Six Sigma Champion (Sponsor) for Organization and for self-career:
• Champions set the direction of process improvements in the organization. They link the
benefits of the project to organizational priorities.
• Champions can create a portfolio of projects which could range from projects in Customer
Satisfaction, Service, Cost and Quality. It provides the Champions the visibility in the
process and also showcases his abilities to top-management to manage varied portfolio of
projects.
SIX SIGMAS master’s BLACK BELT (MBB):
These individuals are responsible for translating the high-level business goals into a Six
Sigma strategy for the division and the supporting tactics. They work with the deployment
leader to achieve the former. They also lead the development of the Six Sigma skills in the
organization, for Black Belts, Green Belts, and the general associate base. MBB’s have
ultimate responsibility to ensure the quality, value, and sustainability of Six Sigma projects
under their guidance.

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MBB’s are responsible, together, for the success of the overall Division’s Six Sigma effort.
They coordinate and lead activity on key cross-division value streams (e.g. Customer
Service, Cycle Time, Research, etc). They also ensure that a culture that values openness,
creativity and challenging the status quo develops in the organization.
Deliverables of a Master Black Belt:
• Six sigma strategy and roll-out plan in the organization/function
• Manage Project of the function
• Mentor Teams
• Achieve Lean Six Sigma Results
• Cross-Functional Leadership
• Project Execution and Removing Roadblocks
Benefits of being a Master Black Belt for Organization and for self-career:
• MBB helps to set the culture of Six Sigma right from the grass-root level in the
organization.
• Black Belts are benefited due to the mentoring and statistical skills of MBB.
• MBB can grow up the ladder and become the Chief Quality Officer as he gains experience
and expertise in the field of Six Sigma.
SIX SIGMAS BLACK BELT (BB):
Six Sigma BB’s are full-time/part time project leaders and mentors of the business, including
Green Belts and other associates. They have tactical responsibility for executing specific projects
and ensuring that the results are captured, the changes are owned by the Champions (Sponsors),
and the changes are sustained. They will also lead Six Sigma knowledge transfer to both full-
and part-time participants.
BB’s are expected to create an environment of open, honest debate of facts. They challenge the
status quo where appropriate and share (and seek) ideas across boundaries.
Deliverables of a Black Belt:
• Six sigma strategy and roll-out plan for the given process/area
• Execute Projects
• Help and guide Project Resources/ Help remove project level Barriers
• Team and Project Structuring
• 6 sigma Project Results
• Mentor Green Belts
• Share Best Practices

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Benefits of being a Black Belt for Organization and for self-career:
• BB’s are responsible for taking the process improvements to the next level in the
organization.
• BB’s are highly trained on improving results for the organization using statistical analysis
and Six Sigma tools. Hence, they have a very lucrative career path ranging from Business
Analysts to Process Improvement experts.
SIX SIGMAS GREEN BELT (GB):
Six Sigma Green Belts are the engine of Six Sigma projects. Black Belt’s support the efforts of
the broader business teams to identify and implement change. The GB’s are part-time Six Sigma
Project Leaders. They are responsible for scoping the projects, leading the project team, calling
for help when needed, managing interfaces with business leaders, and ensuring sustainable
results.
The goal of GB’s is to translate the value of Six Sigma to the specific work environment and
problems.
Deliverables of a Green Belt:
• Project Execution
• Team and Project Structuring
• Six Sigma Project Results
• Share Best Practices
Benefits of being a Green Belt for Organization and for self-career:
• GB’s have authority in their respective processes and can get the work done effectively.
This is a very critical aspect for the organization as it builds its process improvement
structure within each process.
• For self-career, GB’s receive exposure to senior management directly by virtue of the
projects and get the opportunity to make a difference in the organization.
SIX SIGMAS YELLOW BELT (YB):
These are the project-specific, full-or part-time resources that provide process and cross-
functional knowledge, as well as help to sustain the gains. They have co-ownership of the project
with the Six Sigma Experts and are responsible for the quality of the work and results.
This team also plays the critical role of translating the process gains from Six Sigma to other
areas of the business after the specific project has been completed. This is the true leverage of
Six Sigma methodology!

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Deliverables of a Yellow Belt:
• A Yellow Belt has basic knowledge of Six Sigma
• They do not lead projects on their own, as does a Green Belt or Black Belt.
• YB participates as a core team member or subject matter expert (SME) on DMAIC project
or projects. Supports Green Belt or Black Belt in developing process maps, helping with
data capture, facilitating simulation, and improvements.
• YBs may often be responsible for driving smaller process improvement projects using Lean
tools or best practice sharing in their processes.
Benefits of being a Yellow Belt for Organization and for self-career:
• For any project, Yellow Belts are those individuals who are the Subject Matter Experts
(SME’s) of their respective processes and also have the basic know-how of Six Sigma.
They are the spokes of a wheel and can help drive any Six Sigma process to closure by
using their process expertise. Organizations can greatly benefit by choosing the right YB’s
for the right projects.
• For self-career, YB’s get exposure of channelizing their Subject knowledge to process
improvement opportunities yielding tremendous benefits for self-understanding.
Example of a Mobile Phone factory which intends to transition to Six Sigma methodology in
a mobile phone factory:
Functional Roles vs Six Sigma Roles
Criticism
Lack of originality
Quality expert Joseph M. Juran described Six Sigma as "a basic version of quality improvement",
stating that "there is nothing new there. It includes what we used to call facilitators. They've
adopted more flamboyant terms, like belts with different colors. I think that concept has merit to

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set apart, to create specialists who can be very helpful. Again, that's not a new idea. The American
Society for Quality long ago established certificates, such as for reliability engineers."[26]
Inadequate for complex manufacturing
Quality expert Philip B. Crosby pointed out that the Six Sigma standard doesn't go far enough[27]
—
customers deserve defect-free products every time. For example, under the Six Sigma standard,
semiconductors which require the flawless etching of millions of tiny circuits onto a single chip
are all defective, he claims.[28]
Role of consultants
The use of "Black Belts" as itinerant change agents has fostered an industry of training and
certification. Critics have argued there is overselling of Six Sigma by too great a number of
consulting firms, many of which claim expertise in Six Sigma when they have only a rudimentary
understanding of the tools and techniques involved or the markets or industries in which they are
acting.[29]
Potential negative effects
A Fortune article stated that "of 58 large companies that have announced Six Sigma programs, 91
percent have trailed the S&P 500 since". The statement was attributed to "an analysis by Charles
Holland of consulting firm Qualpro (which espouses a competing quality-improvement
process)".[30]
The summary of the article is that Six Sigma is effective at what it is intended to do,
but that it is "narrowly designed to fix an existing process" and does not help in "coming up with
new products or disruptive technologies."[31][32]
Over-reliance on statistical tools
A more direct criticism is the "rigid" nature of Six Sigma with its over-reliance on methods and
tools. In most cases, more attention is paid to reducing variation and searching for any significant
factors and less attention is paid to developing robustness in the first place (which can altogether
eliminate the need for reducing variation).[33]
The extensive reliance on significance testing and
use of multiple regression techniques increases the risk of making commonly unknown types of
statistical errors or mistakes. A possible consequence of Six Sigma's array of P-value
misconceptions is the false belief that the probability of a conclusion being in error can be
calculated from the data in a single experiment without reference to external evidence or the
plausibility of the underlying mechanism.[34]
One of the most serious but all-too-common misuses
of inferential statistics is to take a model that was developed through exploratory model building
and subject it to the same sorts of statistical tests that are used to validate a model that was specified
in advance.[35]
Another comment refers to the often mentioned Transfer Function, which seems to be a flawed
theory if looked at in detail.[36]
Since significance tests were first popularized many objections
have been voiced by prominent and respected statisticians. The volume of criticism and rebuttal
has filled books with language seldom used in the scholarly debate of a dry subject.[37][38][39][40]

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Much of the first criticism was already published more than 40 years ago. Refer to: Statistical
hypothesis testing Criticism for details.
Articles featuring critics have appeared in the November–December 2006 issue of USA Army
Logistician regarding Six-Sigma: "The dangers of a single paradigmatic orientation (in this case,
that of technical rationality) can blind us to values associated with double-loop learning and the
learning organization, organization adaptability, workforce creativity and development,
humanizing the workplace, cultural awareness, and strategy making.
Nassim Nicholas Taleb considers risk managers little more than "blind users" of statistical tools
and methods. He states that statistics is fundamentally incomplete as a field as it cannot predict the
risk of rare events — something Six Sigma is especially concerned with. Furthermore, errors in
prediction are likely to occur because of ignorance for or distinction between epistemic and other
uncertainties. These errors are the biggest in time variant (reliability) related failures.
Stifling creativity in research environments
According to an article by John Dodge, editor in chief of Design News, use of Six Sigma is
inappropriate in a research environment. Dodge states[44]
"excessive metrics, steps, measurements
and Six Sigma's intense focus on reducing variability water down the discovery process. Under
Six Sigma, the free-wheeling nature of brainstorming and the serendipitous side of discovery is
stifled." He concludes "there's general agreement that freedom in basic or pure research is
preferable while Six Sigma works best in incremental innovation when there's an expressed
commercial goal."
A BusinessWeek article says that James McNerney's introduction of Six Sigma at 3M had the effect
of stifling creativity and reports its removal from the research function. It cites two Wharton School
professors who say that Six Sigma leads to incremental innovation at the expense of blue skies
research. This phenomenon is further explored in the book Going Lean, which describes a related
approach known as lean dynamics and provides data to show that Ford's "6 Sigma" program did
little to change its fortunes.
Lack of systematic documentation
One criticism voiced by Yasar Jarrar and Andy Neely from the Cranfield School of Management's
Centre for Business Performance is that while Six Sigma is a powerful approach, it can also unduly
dominate an organization's culture; and they add that much of the Six Sigma literature – in a
remarkable way (six-sigma claims to be evidence, scientifically based) – lacks academic rigor:
One final criticism, probably more to the Six Sigma literature than concepts, relates to the evidence
for Six Sigma’s success. So far, documented case studies using the Six Sigma methods are
presented as the strongest evidence for its success. However, looking at these documented cases,
and apart from a few that are detailed from the experience of leading organizations like GE and
Motorola, most cases are not documented in a systemic or academic manner. In fact, the majority
are case studies illustrated on websites, and are, at best, sketchy. They provide no mention of any
specific Six Sigma methods that were used to resolve the problems. It has been argued that by

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relying on the Six Sigma criteria, management is lulled into the idea that something is being done
about quality, whereas any resulting improvement is accidental (Latzko 1995). Thus, when looking
at the evidence put forward for Six Sigma success, mostly by consultants and people with vested
interests, the question that begs to be asked is: are we making a true improvement with Six Sigma
methods or just getting skilled at telling stories? Everyone seems to believe that we are making
true improvements, but there is some way to go to document these empirically and clarify the
causal relations.