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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