Six Sigma
Jason Cummins
Department of Software Engineering
University of Wisconsin – Platteville
Platteville, WI 53818
cumminsj@uwplatt.edu
Abstract
Six Sigma is a quality assurance/improvement process which can be adapted into every
production process. It was developed by Motorola in 1985, but really took off in 1995 when Jack
Welch announced that GE would be launching Six Sigma in order to create the best quality
products in the world. Six Sigma was created in order to reduce the variance in processes but it
also improves the quality of process outputs by identifying and removing the causes of errors. A
business will be completely utilizing a Six Sigma process when 99.99966% of its products are
defect free. Six Sigma projects follow two different methods; the first is a project to improve the
existing process and the second s used in creating a new product or process.
Introduction
Six Sigma is a disciplined quality improvement approach to greatly increase a business’s
products and process. Its goal is to detect and eliminate defects which in turn will increase
customer satisfaction as well as reduce the cost of the business’s creation process[Six Sigma
Framework]. The original Six Sigma comes from the idea that if there are six standard deviations
between the process mean and the nearest specification limit then essentially no items will fail to
meet the requirements. There is also a fascinating way in which Six Sigma roles are determined;
it loosely follows martial arts rankings. The two methodologies that Six Sigma follows is also
based off of the standard Deming’s Cycle each of which are composed of five phases. Lastly
there is a great tool which provides an easy execution of a Six Sigma Project called Six Sigma
Project Management Tool(SSPMT).
History of Six Sigma
The origin of Six Sigma can date back to a long time ago, almost to the origin of standard
deviation, depending on how it is interpreted. Whether some believe that it originated with Carl
Gauss’s introduction to the concept of the normal curve or when Walter Shewhart showed that
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three sigma from the mean is the point in which a process has errors. Most people would accredit
the start of Six Sigma to Motorola who found that their traditional way of measuring defects was
not good enough and decided to come up with this new methodology. Since then Six Sigma has
become an extremely popular method to improving processes in all types of businesses [1].
Six Sigma Roles
There are several distinct roles in Six Sigma that loosely follow that of martial arts titles. The
titles are as follows: Green Belt, Black Belt, Master Black Belt, and Champion. Different
companies seem to have some small changes in roles or inclusions of new roles such as a
Sponsor or Process Owner but the original four titles seem to be the most commonly recognized
in the Six Sigma process.
Green Belt
Green Belts are generally on the lowest level of the Six Sigma totem pole. The only ones below
them are the Team Members who are just aware of the Six Sigma project but have no real
training in it. The Green Belts are generally lower level management who has had a few weeks
of training in Six Sigma and they generally are in charge of smaller projects for the company or
are part of a Black Belts project. Green Belts are generally leaders of a certain department but
individuals in the team can also have the role. The projects that the Green Belts take on are
almost always Define, Measure, Analyze, Improve, and Control (DMAIC) [1].
Black Belt
Black Belts have some more responsibility than the Green Belts. They are expect to have at least
a month’s worth of classroom time devoted to learning Six Sigma techniques. Generally a Black
Belt will be assigned the role for an extremely large project that would take somewhere from one
to two years to complete. It is also the Black Belt’s responsibility to help guide the Green Belts
and help develop them as Six Sigma leaders. A great Black Belt needs to have superb
quantitative and analytical skills. They must also have the ability to see the big picture and needs
of all the stakeholders in the projects they oversee. Most Black Belts must be officially certified
in order to ever receive the position as a Black Belt in their company [1].
Master Black Belts
The Master Black Belt role is given to a certified Black Belt who has proven themselves and is
able to train and coach other Black Belts and Green Belts. A Master Black Belt should also be
able to guide leaders in creating a strategy which follows the Six Sigma Principles. The Master
Black Belt is someone who has managed many projects and is an expert at using the Six Sigma
methods and tools [1].
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Champions
Champions are generally senior level executives who will sponsor a specific six sigma project.
Their responsibility is to make sure that the project gets all the resources it requires and to solve
any possible issues that come up between Black Belts or Master Black Belts. The Champions are
also sometimes considered as a Sponsor. The Champions are required to have a high-level
understanding of the Six Sigma process and should be actively leading the company to fully
implement Six Sigma [1].
Six Sigma Methodologies
There are generally two different methodologies that the Six Sigma process uses. The first
methodology is called DMAIC which is used for existing process improvements. The second
methodology is called DMADV or DFSS(“Designs For Six Sigma”) which is used for creating
new product or process designs. Each methodology has five distinct phases and was originally
inspired by the Deming’s Cycle as seen in the following diagram. Every Six Sigma phase is
expected to take about a month of time to complete.
Figure 1: Deming’s Cycle
DMAIC
The DMAIC methodology stands for Define, Measure, Analyze, Improve, and Control. The
methodology is to be used to improve an already existing business process. It is the most widely
used methodology of Six Sigma since most businesses will seek to improve their process rather
than create a new one from scratch. Generally all of the different levels of Six Sigma leaders
know and use this method.
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Define
The first phase is to define the problem, during this phase is when working with the customers to
determine requirements is required, figure out the business goals, and finalize the scope of the
project. Some of the different tools required during this phase include a process mapping tool,
project charts, and any other requirement tools one may think of. It is imperative during this
phase that all critical to quality areas are defined; this will help improve the process greatly [5].
Measure
The second phase is measuring the data that you have. This includes collecting the data on
current processes and making sure the data that has been gathered is valid. With the measured
data it becomes possible to evaluate the projects process performance. The objective of this
phase is to come to a complete understanding of why, how, and where defects are being created.
The team will use a variety of statistical tools to identify the key areas of your code that are
causing defects [5].
Analyze
The third phase requires the data to be analyzed that was collected from the previous phase. Then
identify ways to improve the process so that it’s closer to how efficient the team required it to be
during the define phase. During this phase the root of the poor sigma performance of the current
process will be found [5].
Improve
The next phase is to improve the current process using all the knowledge gained from the
previous two phases. The team will come up with several different solutions to the problems in
the process which was found during the analysis portion and will work together to determine
which solution would work the best [5].
Control
The final phase in this methodology is called control. In this phase the team will work to
implement the solutions determined by the previous phase as well as make sure that maintenance
is improved so that the six sigma performance will not wither in the future [5].
DMADV
The DMADV or DFSS methodology is similar to the DMAIC except that it is for creating a
completely new process rather than improving an already existing process. This is a much more
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challenging methodology in Six Sigma. You will generally only find Master Black Belts and
some other Black Belts who have some experience attempt to create a process from scratch using
this Six Sigma methodology. There are occasions when a DMAIC project ends up turning into a
DMADV project just because it is better to start from scratch than improve upon what is already
there [3].
Define
The first phase is the same as the first phase of DMAIC. It is the define stage where the team
needs to identify the scope and deliverables of the project. This is an extremely important first
step which should be done carefully in order to minimize possible errors in the future
deployment of the process [3].
Measure
The next stage is measure where the team will gather information for the design efforts. The
purpose of this stage is to pinpoint critical to quality factors for the design phase. This phase is
much more difficult to measure the critical to quality factors since this is a completely new
process and there is no older process to measure the results against [3].
Analyze
The third stage, analyze, is where solutions must be generated for the process based off of the
measurements gained from the previous phase. Then after figuring out as many solutions as
possible the team will take all the solutions attained and work together to create the best solution
possible [3].
Design
The next stage is the design phase. During this phase the solutions from the previous phase will
be created and then implemented to make a prototype. In this phase it is a necessity to make sure
all the critical to quality factors in the process have been accounted for and are designed so that
they will not fail in the future [3].
Verify
The final stage is the verify phase. The verify phase is used to make sure that the designed
solutions will fulfill all requirements from the Define phase and will yield great performance at
all the critical to quality areas [3].
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Six Sigma and CMMI
There are many misconceptions about Six Sigma, one of which is that it is a competitor to
CMMI and other standards. This is simply not true; Six Sigma is not domain specific like many
of the other process models and standards and therefore can be used in conjunction with the other
models. Six Sigma can be used to help improve on an already existing model. In fact many
organizations have started integrating CMMI with Six Sigma in order to achieve a higher level of
maturity. Some areas of CMMI integrate extremely well with Six Sigma already for instance, the
Quantitative Process Management and Casual Analysis & Resolution process areas are
extremely similar to what needs to be done in the DMAIC methodology of Six Sigma. Six Sigma
can be implemented at any maturity level in order to achieve any higher level of maturity, but it
is best to start integrating at a lower level of maturity. One technique to use both CMMI and Six
Sigma together is to use CMMI in order to create processes based off of the community best
practices and then implement Six Sigma in order to optimize the process. Six Sigma reinforces
mission focus, and its enterprise deployment strategy fosters culture change that is supportive of
CMMI implementation. The following chart can show where Six Sigma can be used in each
level of maturity in CMMI [2].
Figure 2: Six Sigma in CMMI
Six Sigma Software Architecture
In order to use/create a six sigma software tool one must understand the architecture of Six
Sigma. The architecture that will be discussed will follow the DMAIC methodology. One
example of a tools architecture is from the Six Sigma Project Management Tool(SSPMT). They
follow a fairly basic architecture which has four layers. The first layer is the Six Sigma Project
Execution Layer. This layer follows the flow of the DMAIC methodology and its five phases.
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This layer also holds all of the different tools needed to define, measure, and analyze the process.
The next layer is the Six Sigma Project Supporting Layer. This layer holds the user and role
management section which helps manage the different roles that was discussed
earlier(Champion, Master Black Belt, Black Belt, Green Belt). It also has the six sigma project
tracking which gives the user traceability to track the progress of their project. Another piece on
the supporting layer is the project report generation, which as it sounds like will take the
analyzed results and create a report for you. The third layer is the project data layer which holds
the data repository. This layer will store all of the collected data as well as the analyzed results
during the Six Sigma projects. The final layer is the integration layer which will allow the user to
integrate with other applications such as other quality assurance programs. A visual aid of the
architecture can be seen in the image below [5].
Figure 3: Six Sigma Software Architecture
Benefits of Using Six Sigma
Just about every company that uses Six Sigma has yielded great benefits from it. There are
positive reports from many large companies such as Motorola, General Electric, and Allied
Signal/Honeywell [4]. One of the most common benefits is that Six Sigma allows project
managers to come up with numerous solutions to a large range of possible issues which allows
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future predictions of problems to be much simpler. These improvements help companies become
extremely efficient and more productive which in the long run saves them millions or possibly
billions of dollars. Unlike many other process improvement methodologies Six Sigma is much
more rapid and can yield greater results more quickly. It completely envelopes the entire
organization using it and makes it so that managers and leaders have to take a much closer look
at the inner workings of their companies [6].
Issues with Six Sigma
Even though Six Sigma does bring in large profits if it is successful there can be some problems
with it. The majority of these problems occur when an organization isn’t fully immersing itself in
the Six Sigma ideology. For instance if a company doesn’t fully commit to sending all of their
managers to Six Sigma training there is a very large chance that the people they do send won’t be
able to convey the needs of Six Sigma completely. Also Six Sigma can fail if managers who are
expendable from main stream activities are chosen because they may not have the sufficient
abilities to lead such a complicated project. Another possible issue occurs when companies are
not willing to allow for a proper amount of training in their Black Belt leaders. This leads to the
Six Sigma process becoming a side activity that is overlooked and then they gain none of the
benefits of Six Sigma [4].
Conclusion
The Six Sigma methodology has proven invaluable to all the companies who have used it
correctly and have immediately seen its benefits. The easy to follow steps between either the
DMAIC or DMADV methodology allow the process to create rapid improvement among any
process that is being looked at from just about any field. The roles that are taken among the
managers whether they are Green, Black, or Master Black Belts clearly define their
responsibilities and capabilities in the Six Sigma process. Finally Six Sigma is not a competitive
standard with CMMI but rather can be integrated with it to help improve maturity levels of
companies. So all in all Six Sigma is an amazing methodology which will greatly improve any
company that can fully commit to its ideas.
References
[1] Ideal Meadia LLC. i Six Sigma. Retrieved 3/08/2012. <http://www.isixsigma.com/>
[2] Siviy, Jeannine; Penn, M. Lynn; Harper, Erin. “Relationships Between CMMI and Six
Sigma”. Software Engineering Institute 2005. Retrieved 3/08/2012. <http://www.sei.cmu.edu/>
[3] Franza, Richard; Chakravorty, Satya. “Design for Six Sigma(DFSS): A Case Study”.
Kennesaw State University, Dept. of Management and Entrepreneurship 2007. Retrieved
3/10/2012. http://ieeexplore.ieee.org/
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[4] Catherwood, Philip. “Champions of the cause”. Waterton Technol. Centre, UK 2005.
Retrieved 3/12/2012. http://ieeexplore.ieee.org/
[5] Pan, Zhedan; Baik, Jongmoon. “A Six Sigma Framework for Software Process
Improvements and its Implementation”. Asia-Pacific Software Engineering Conference.
Retrieved 3/12/2012. http://ieeexplore.ieee.org/
[6] Aveta Business Institute. Six Sigma Online. Retrieved 3/14/2012.
<http://www.sixsigmaonline.org>