Question Details
(solution) Quality Engineering, 22:299-305, 2010 Copyright # Taylor &
Read the article: Goh, T. N. (2010). Six Triumphs and Six Tragedies of Six Sigma. Quality Engineering, 22(4), 299-305. doi:10.1080/08982112.2010.495102. (attached)
Respond to the discussion questions:
Which ?triumph? would have the greatest impact for a successful Six Sigma implementation to improve supply chain management processes? Explain your position.
Which ?tragedy? taught you something new and valuable?
Which ?tragedy? have you seen before in other business scenarios?
Quality Engineering, 22:299?305, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 0898-2112 print=1532-4222 online
DOI: 10.1080/08982112.2010.495102 Six Triumphs and Six Tragedies
of Six Sigma
T. N. Goh
Industrial and Systems
Engineering Department,
National University of Singapore,
Singapore ABSTRACT Six Sigma as a quality improvement framework has enjoyed an
unprecedented long period of popularity. This article brings out factors
that contribute to the uniqueness of Six Sigma, with its extensions and
derivatives such as Design for Six Sigma and Lean Six Sigma. Those features
that have brought about an impetus for quality improvement are regarded as
??triumphs?? of Six Sigma, whereas some worrying trends in the practice of
Six Sigma are labeled as ??tragedies.?? Clearly, industry should leverage on
the strengths of Six Sigma and be careful not to become unwitting victims
of the weaknesses. A realistic and balanced view is certainly called for at this
juncture, and the advantages and pitfalls associated with Six Sigma should
be fully recognized if Six Sigma is to continue its ??winning streak?? of the past
quarter of a century.
KEYWORDS Design for Six Sigma, Lean Six Sigma, quality engineering, quality
management, Six Sigma, statistical thinking INTRODUCTION Address correspondence to T. N. Goh,
Industrial and Systems Engineering
Department, National University of
Singapore, 10 Kent Ridge Crescent,
Singapore, 119260. E-mail:
[email protected] Some 20 years ago, at the height of popularity and controversy of the
so-called Taguchi methods?exemplified by Taguchi (1986)?an article
by Pignatellio and Ramberg (1991) appeared in Quality Engineering pointing out the positive and negative aspects of the Taguchi version of quality
engineering and experimental design, with the euphoria in industry at that
time as a backdrop. Today, Taguchi is no longer on the lips of quality
engineers and managers?at least, it is not deemed fashionable anymore
to talk about it. In fact, ??consultants?? can no longer make easy money
by repeating the NBC mantra ??If Japan can, why can?t you??? With the
recent great Toyota automobile recalls, from now on even the ??Toyota
Method?? of production probably will have to be put on the back burner
at least for some time. This article addresses a subject that is all American,
something that has replaced Taguchi method as the most talked-about
quality improvement approach for almost two decades. This is, of course,
Six Sigma, on which there has been such an abundance of literature that
elaboration on its contents would be unnecessary?see, for example,
Harry and Schroder (1999), Hahn et al. (2000), Goh (2002), and Brady
and Allen (2006).
299 Six Sigma, in the course of its development, has
generated a number of derivatives and extensions,
such as Design for Six Sigma?e.g., Tennant
(2002)?and Lean Six Sigma?e.g., George (2002).
In this article, the term Six Sigma covers all these
variants collectively because they share basically
the same analytical foundations, with similar modes
of application. Regardless of the variant, Six Sigma
has commanded wide attention in industry and,
much like the Taguchi phenomenon in the 1980s,
success stories abound in many publications; detractors inevitably also have their say from time to time;
for example, Lee (2001), Schrage (2001), Morris
(2006), and Mika (2006). However, arguments
against Six Sigma such as these are not usually
made on rigorous grounds; likewise, promoters of
Six Sigma tend to offer casual promises such as
??Savings can hit $300 K per project, so a single Black
Belt can potentially bring a company $1.2 million to
the good annually?? (Harry and Crawford 2005).
Thus, some realistic assessment of ??all things Six
Sigma?? at this juncture would not be out of place,
in view of the surge of interests in Six Sigma in industry on one hand and the considerable investments
made by companies in manpower development
and external expertise on the other. Only with better
understanding of the subject could an organization
leverage on Six Sigma?s strengths and overcome its
weaknesses and be able to answer this question with
confidence: ??To Six Sigma, or not to Six Sigma??? WHAT QUALIFIES TO BE MENTIONED
Just as Pignatellio and Ramberg (1991) effectively
used the ??triumphs?? and ??tragedies?? categorization
to highlight the notable aspects of Taguchi methods,
a similar approach is taken here with respect to Six
Sigma. Discussions of features of Six Sigma abound
in the literature, such as Hahn (2005), but presented
here will be the most important facts that an individual or company ought to know about Six Sigma.
For this reason, only six of each category are brought
up, though the lists could be readily extended.
Some explanation of these categories is in order.
What constitutes a triumph? Basically, a triumph
exists when in the field of quality engineering there
has not been a similarly meritorious approach or
methodology before; the item in question must be
able to lead to a significant impact or paradigm shift,
T. N. Goh with results that are of practical value; that is, not just
a theoretically elegant scenario. What, on the other
hand, qualifies as a tragedy? The answer is any
feature that, if unchecked, could negate a triumph,
create misguided or misled actions, or even destroy
what originally has been useful. The selection of
six items in each category is by no means definitive
or unique and has been made largely based on the
author?s personal experience in training, consulting,
and research in Six Sigma over many years. Because
the relative significance of each item is a matter of
personal opinion, there is no particular order in
which the items are presented in the following
sections. SIX SIGMA TRIUMPHS
Triumph No. 1
Use of a common, realistic metric for quality
assessment and improvement: The use of critical-toquality (CTQ) and defects per million opportunities
(dpmo) as performance indices is a trademark of
Six Sigma. Deliberations on the choice and definition
of CTQ would help focus on the meaningful and
avoid the inconsequential. As a yardstick for measure
of performance, dpmo allows ready comparisons of
performance such as one process versus another,
before versus after, as well as cross-process comparative studies. This is also associated with an
equivalent yardstick, namely, sigma level that can
be used for purposes such as benchmarking and
project target setting. It may be noted, though, that
not all outcomes are binary (??defective?? or ??nondefective??), and in some cases even a binary classification can be arbitrary (e.g., the time it takes to
respond to a certain category of customer request).
The important point is that, for the first time, ??zero
defect?? is no longer an often-spoken-of but elusive
goal (or worse, a lip service); instead, one is supposed to face the realistic challenges of non-zero
defect situations squarely. This is an important paradigm shift, with which the nebulous promise of zero
defect is abandoned, though serious efforts are made
(with effective infrastructure and tools, as detailed in
the descriptions of other ??triumphs?? later on) to inch
toward that goal. Furthermore, with Six Sigma, there
are now generic metrics for marking progress; the
defect measurements in the hands of the quality
300 practitioner transcend processes and industries of
different nature. Generally, concepts expressed in
terms of dpmo and sigma levels can be more readily
explained and accepted by management than more
formal mathematical jargons. Triumph No. 2
Clear assignment of roles and responsibilities in
performance improvement efforts: Another important
paradigm shift that comes with Six Sigma is ditching
of the refrain ??Quality is Everybody?s Business.?? The
intent of this statement may be good and valid, but in
the real world this could be taken to imply diffused
responsibilities, especially whenever there are problems, with the assumption that everybody is equally
capable of handling quality issues. It is well known
that in many situations, ??Everybody?s Business?? in
the end could degenerate into ??Nobody?s Business.??
Not so in Six Sigma; personnel with various
degrees of training and experience are designated
clearly, and there are now individuals recognized
to know more tools than others when it comes to
performance improvement or problem solving.
Thus, there is a commonly acknowledged hierarchy
of people: Champions?Master Black Belts?Black
Belts?Green Belts?Yellow Belts that have different
professional responsibilities in an organization. In
addition, the success of Six Sigma depends largely
on top management leadership rather than the previous ??bottom-up?? concepts: quality control circles,
for example, may still have their place in handling
specific local problems, but they cannot be the staple
diet for fundamental organizational performance
enhancement and customer satisfaction. Triumph No. 3
Logical alignment of statistical tools: The concept
that ??the whole is larger than the sum of the parts??
cannot be truer when it comes to the deployment
of statistical tools in Six Sigma. Many an academic
has pronounced that there is ??nothing new?? in Six
Sigma. This is true when Six Sigma methodologies
are taken apart; for example, distribution functions
describing variability have been described in detail
in many books before, process capability analysis is
a known and used concept, analysis of variance
is recognized by every student of statistics, gage
301 repeatability and reproducibility study is an
established procedure, design of experiments is not
a fresh concept, control charts have been applied
for decades . . . and indeed there are already plenty
of well-established college courses or on-the-job
training programs on these subjects. So, what?s new?
What is new, as offered by Six Sigma, is the alignment and integration of statistical tools?heretofore
taught and learned in a disjointed manner?into a
logical, purposeful sequence for CTQ improvement
and business competitiveness. Specifically, the
tools are built into a Define?Measure?Analyze?
Improvement?Control (or DMAIC) framework that
suggests, for example, that a process be optimized
via statistical design of experiments in the Improve
phrase before being sustained by control chart applications in the Control phrase?instead of drawing
up a control chart for something that is not even
known to be optimal or otherwise. In fact, in pre-Six
Sigma days, the more effective the control chart, the
longer the continuation of some nonoptimized process. In other words, Six Sigma makes statistics work
harder (by seeking the optimal) and smarter (by
focusing on the best) in the hands of nonstatisticians. Triumph No. 4
Recognition of the time effects on processes: Talking about the use of statistics by nonstatisticians?
in the past, for understandable reasons, practically
only time-invariant models are used by the rank-andfile. Six Sigma does not provide the full answer to the
consequences of time-dependent natural changes,
but it does bring up the concept of short-term
versus long-term variation; that is, the ??1.5 sigma
shift?? in the assessment of dpmo and sigma levels.
Although the rationale for such a shift is an unresolved issue (see, for example, ASQ Discussion
Boards [2005]), the fact remains that Six Sigma is
the only quality improvement approach that prominently recognizes and fully takes into account what
any experienced quality practitioner must have
faced: the relentless realization of the second law
of thermodynamics, meaning ??Things left to themselves will deteriorate.?? No procedures, formulated
by textbooks or otherwise, prior to the advent of
Six Sigma required practitioners to express this real
and important phenomenon explicitly up front.
Regardless of the exact nature of a process one
Six Triumphs and Six Tragedies of Six Sigma is handling, this is an insightful defensive and
preemptive move. Triumph No. 5
Unprecedented synergy with modern information
technology: Six Sigma attained its popularity among
practitioners because it arrived at the right time.
Should Six Sigma have appeared on the scene, say,
20 years earlier than the mid-1980s, it would not take
off because it is statistics based?the shear amount of
data crunching would mean that only dedicated
personnel hired to crank big and noisy mechanical
calculators would want to have anything to do with
it. Many have lamented the nonuse of statistics in
industry, for example, Penzias (1989), but few have
admitted the real and perceived obstacles, namely,
the efforts it would take to gather, store, transform,
and analyze data in industrial settings.
By the 1990s, with the appearance and swift
prevalence of both hardware and software brought
about by the age of information technology, that is,
personal computers, notebook computers, with
user-friendly versions of the likes of MINITAB and
JMP, application of Six Sigma no longer demands
deep knowledge of statistical theory or superior data
processing capabilities. The credit may not entirely
lie in the contents of DMAIC, but winning over
hesitant onlookers and converting industry people
into aficionados of statistical tools is an undeniable
triumph of Six Sigma. Triumph No. 6
Capabilities to grow for larger roles for business
competitiveness: Unlike many other quality tools or
certification systems that remain essentially the same
throughout their useful life, Six Sigma is organic. Six
Sigma as applied in industry today can be a far cry
from the Six Sigma of the 1980s. Through the years,
Six Sigma has been augmented, extended, and
transformed into even more comprehensive frameworks that are applicable all the way from design
to manufacture (of products) or implementation (of
service systems).
Design for Six Sigma and Lean Six Sigma, in a variety of roadmaps in different organizations, are major
examples of the upshot of the ??classic Six Sigma??
formula from Motorola. The former reflects the belief
T. N. Goh that ??Prevention is better than cure,?? and the latter
recognizes that waste elimination should go hand
in hand with variation reduction. There is no apparent limit to what Six Sigma might be morphed into in
the years to come: mass customization, for example
(Piller and Tseng 2010), is one possible direction
for development. In recent years, serious attempts
to introduce Six Sigma into service sectors?government, education, health care, transportation, tourism,
etc.?actually reflect the vitality of Six Sigma and
constitute a veritable triumph over any narrowly
defined and applied procedures for quality. SIX SIGMA TRAGEDIES
Not all things associated with Six Sigma are flawless, however. Some of the unsatisfactory aspects of
Six Sigma are not inherent in Six Sigma itself but in
the way in which Six Sigma is learned or deployed.
Left unchecked, such weaknesses could lead to the
undoing of Six Sigma in the long run. Opinions could
differ, but the accounts given below are based on
what has been observed in industry. Tragedy No. 1
The belief that Six Sigma (as typical Black Belts
know it) is universally applicable: This is related to
the growing extension of Six Sigma applications,
especially to nonmanufacturing systems. Unfortunately, this is where the Achilles? heel of the common
Six Sigma ??body of knowledge?? exhibits itself?even
though the training of Six Sigma workers has been a
frequent subject of discussion; see Hoerl (2001), for
example. Many run-of-the-mill Black Belts are ignorant of, for example, queuing theory, methods for
discrete observations, as well as the nature of ordinal
scales or correlated observations commonly found in
service systems. Many of them would take on service
quality projects with the idea that they have already
been well prepared by the standard Black Belt
training program.
In principle, it is commendable for a quality professional to try to push the boundaries of Six Sigma
applications. However, Black Belts using conventional Six Sigma procedures on service systems could
end up with results that could not stand up to serious
scrutiny of a good statistician. The problem could
be compounded in some situations where
302 recommendations cannot be tested or demonstrated
because the system in question has already changed
in characteristics or boundaries over the project
duration. The tragedy is doubled if the Black Belts
are not even aware of their own inadequacy or
limitations and, instead, brandish to management
or customers the outcomes of half-baked studies. Tragedy No. 2
Obsession with personal attainments: As in many
other situations, the means could gradually and
unwittingly become the end. Witness the myriad
of overprized (or, interestingly in some cases,
discounted) commercial Black Belt or Green Belt
training programs that promise ??certification?? at the
end. It seems forgotten that customers? benefits,
and ultimately an organization?s business interests,
were the very motivation for Six Sigma originally.
This is where some CTQ ought to be defined: is Six
Sigma meant to benefit an organization?s customers
or a certification project owner?
Because Six Sigma calls for a hierarchy of professionals with a differentiation in levels of expertise
and responsibilities, designation by different colors
of ??belts?? is useful. However, most advertisements
today for Six Sigma training and many potential
takers seem to treat certification to a belt of a certain
color to be the sole objective; the brutal fact is that
classes are nowadays offered with individuals?
improved re´sume´s as the unabashed motivation,
rather than any customer?s improved satisfaction or
any organization?s improved bottom line. A practice
has already been observed that presents ??BB?? or
??MBB?? in a re´sume´ as it were a professional degree,
rather than a role within Six Sigma implementation. Tragedy No. 3
The idea that professional statisticians are no
longer needed: The main feature that contributes to
the triumphs of Six Sigma could become an inhibitor
of further successes. Many Six Sigma workers, particularly freshly minted Black Belts, tend to have the
idea, albeit an implicit one, that the tools entailed
in DMAIC are both necessary and sufficient for problem solving in the real world. (Tragedy No. 1 thus
comes to mind again). The certification process, if
anything, helps foster this misconception because it
303 implies that an individual is now ??fit?? to handle Six
Sigma implementation; in reality, all it means is that
the person has satisfied certain requirements prescribed by anything from an established organization
such as ASQ to a fee-grabbing consulting outfit with
unknown track record.
Admittedly, some enlightened trainers and their
learners are aware of the ocean of knowledge and
tools left untouched during the standard Six Sigma
training: a well-designed training program would
use the Pareto principle to emphasize to the trainees
that what is covered, the vital 20%, is actually not
always needed, whereas the rest, 80% of other tools
not in the DMAIC syllabus, are not really all ??trivial??
and occasionally have to be called for?for that, help
from professional statisticians would certainly be
needed. For a fuller discussion, see, for example,
Hahn and Hoerl (1998). Tragedy No. 4
Irresponsible hype of Six Sigma: Many, especially
managers, are attracted by easy benefits casually promised by Six Sigma promoters, many of whom nowadays could be entirely commercially motivated. For
example, it remains to be proven whether seductive
statements such as this are scientifically supported:
??As much as $175,000=project and $1 million=yr=
Black Belt?? (Harry 1998; interestingly, one may note
the inconsistency between this promise and the
statement quoted in the Introduction section of
this article). It is real, though, that exorbitant
amounts tend to be quoted by many commercial
training-cum-certification offerings. Other ??motivators?? include descriptions, accompanied by data
and graphs, of enviable rises in stock prices that only
??Six Sigma companies?? would enjoy, though the fact
was that during the early 1990s, there was a general
rise in stock prices in the United States, and practically all prices dipped toward the end of 2008,
Six Sigma or no Six Sigma! There actually was a
formal study on this subject some time ago (Goh
et al. 2003).
Because the likes of General Electric are invariably
held up as models for Six Sigma implementation, for
example, Snee and Hoerl (2003), the practice begs
the question as to whether only organizations with
the scale and operations of General Electric would
benefit from Six Sigma deployment. The upshot is
Six Triumphs and Six Tragedies of Six Sigma likely to be either (a) smaller organizations believe
that Six Sigma is not appropriate for them, therefore
ignoring it; or (b) such organizations are disillusioned when the fancied extraordinary profits turned
out to be ??too good to be true?? and do not materialize?after hefty fees have been paid out and no one
is answerable for the ??failure?? of Six Sigma. If this is
not a tragedy, one wonders what is. A bigoted ??In Data We Trust?? mentality: Precisely
because Six Sigma is data driven, sometimes a practitioner could go overboard with ??statistical evidence.?? Thus, arguments could be advanced in
favor of a course of action on the strength of some
p-value generated by some computer software,
rather than considered opinions based on the experience or insights of business leaders. This is particularly seen in projects presented for certification
purposes: one could get the impression that the
world is ruled by outputs from MINITAB (or such
like), because once some p-value falls within a certain range and the residual checks look passable,
all would seem to live happily ever after. This is
not to say, of course, that different attitudes cannot
be found; a good Six Sigma training program would
produce professionals who are masters, rather than
slaves, of statistical tools and software packages.
In fact, the ??slave?? mentality in Six Sigma is exemplified by a practitioner?s confidence and ability in
handling merely quantitative information. Some
would make a mountain out of a molehill, using data
of dubious quality or data from some poorly constructed or responded survey. Not a few would be
at a loss when encountered with a CTQ that is obviously non-numeric. A quote would suffice to
describe the syndrome and its consequence: ??To
many it will always seem better to have measurable
progress toward the wrong goals than unmeasurable
progress toward the right ones?? (Galbraith 1978).
Apparently the tragedy is not confined to the world
of economists. those wearing ??Belts?? of whatever color in Six Sigma
are expected to conform to the DMAIC straitjacket.
??Quick results?? and ??tangible savings?? are sometimes
engineered to reflect the success of a project?
especially by those associated with the unguaranteed
profit promises, as pointed out previously. This is not
necessarily consistent with customer satisfaction or
business competitiveness, because suboptimization
and short-term benefits could be mistaken as fundamental improvements. Even adherence to, say, the
3.4 dpmo benchmark is not always logical; it could
actually go against customer satisfaction, as pointed
out elsewhere (Conti et al. 2003). A parable on suboptimization can be drawn from a scene in the movie
Titanic, in which one could certainly applaud the
exquisite music performed with seamless teamwork
by the quartet, oblivious of the fact that the ship
was slowly sinking! (In the same vein, one could
ask: would it make sense to throw in Six Sigma manpower to improve the productivity of a mechanical
typewriter assembly line?)
There is one further point that is no less important.
One expectation of Six Sigma is the development of
Black Belts into business leaders of the future. Leaving aside the rigidity of DMAIC (during the
certification-based training anyway), it is clear that
nothing in Six Sigma prepares a Black Belt for technology changes or breakthroughs, technology substitution, lifestyle evolution, or cultural differences.
Furthermore, human attributes that relate to successes are hardly ingredients found in DMAIC:
imagination, vision, passion, insight, judgment, creativity, curiosity, perseverance, just to name a few?
though this is not to imply that none of these has
been seen in actual Six Sigma endeavors. The spirit
of innovation, synergy, breakthrough, and entrepreneurship, for example, could prove to be the prime
mover of an organization, not the behavior of many
a Six Sigma certification seeker. So the point is, it
would be tragic indeed if carefully chosen and
nurtured Black Blacks fail to realize their potential
precisely because of what is lacking in Six Sigma
itself. Tragedy No. 6 CONCLUDING REMARKS Ignorance or neglect of what is important beyond
DMAIC: Six Sigma as commonly practiced is
technology-blind and...
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