1

Six Sigma: a literature review

B Tjahjono*, P Ball, V I Vitanov, C Scorzafave, J Nogueira, J Calleja, M Minguet, L

Narasimha, A Rivas, A Srivastava, S Srivastava and A Yadav

Manufacturing Department, School of Applied Sciences, Cranfield University,

Cranfield, Bedford MK43 0AL, UK

Abstract

Purpose: The purpose of the work presented in this paper is to capture the current

state of Six Sigma as well as to document the current practices of Six Sigma through a

systematic literature review so as to extend and update the previous work of Brady and

Allen (2006).

Design/methodology/approach: The approach to this research is to answer the

questions such as what is Six Sigma?, what are the applications of the Six Sigma?,

what are the main enablers and barriers to its application?, and what are the emerging

trends? These questions are used to guide the search of papers from various

publication databases even if it is expected that existing literature might not be

sufficiently developed to translate each question directly into a finding. The literature is

then analysed and the major emerging themes are presented.

Findings: Seven key findings (topics on which the views of the authors converged) and

two issues (topics on which authors had differing views) have been established. These

include the interpretation of Six Sigma, tools and techniques, implementation of Six

Sigma, benefits, adoption, enablers and links to other disciplines.

Originality/value: The systematic literature review approach used in this paper allows

emerging trends and issues in Six Sigma to be highlighted in a structured and thematic

manner, enabling the future work to progress as Six Sigma continues to develop and

evolve. The findings also open up new opportunities to apply Six Sigma in the fields

that are not widely explored before for instance sustainability and Product-Service

Systems (PSS).

Keywords: Six Sigma, literature review, DMAIC, DFSS, process improvement

Paper type: Literature review

*Corresponding authorAddress: Building 50, Manufacturing Department, School of Applied Sciences,

Cranfield University, Cranfield, Bedford MK43 0AL, UKPhone: +44 1234 750111 ext 5453Email: b.tjahjono@cranfield.ac.uk

2

1. Introduction

Since the introduction of the initial six-step process by Motorola University Design for

Manufacturing training programme in 1988 (Watson and DeYong, 2010), Six Sigma

has evolved to become an extension to Total Quality Management (TQM) (Green,

2006). As a project-driven management approach, the range of Six Sigma applications

is also growing from reduction of defects in an organisation’s processes, products and

services, to become a business strategy that focuses on improving understanding of

customer requirements, business productivity and financial performance (Kwak and

Anbari, 2006). Six Sigma has branched out initially from the electronics industries (e.g.

Motorola and Texas Instruments) to many other sectors. In the last two decades, this

growth has become more prevalent as Six Sigma principles have also been

implemented in service industries in the context of supply chain (Arnheiter & Maleyeff,

2005; Wei et al, 2010), as well as hospitals (Sehwail & DeYong, 2003; van den Heuvel

at al, 2005), local government (Furterer & Elshennawy, 2005) and public sectors (Patel,

S.C. and Zu, 2009; Kumar & Bauer, 2010).

The purpose of this paper is therefore to capture the state-of-the-art within the Six

Sigma philosophy as well as to document notable development of practices through a

systematic literature review. The methodology includes targeting relevant publications

databases, searching these using a wide range of keywords and phrases associated

with Six Sigma, and then reviewing each paper identified. The outcome of these

reviews was the extraction of a set of key findings, compiled and grouped by topics.

2. Research programme

2.1 Scope and research questions

This review of literature, to a large extent, aims to extend the work of Brady and Allen

(2006) who incorporated Six Sigma publications from 1990 to 2003 and complement

3

their findings. For this reason, the systematic literature review in this paper considers a

defined time frame from 2004 to 2009. To provide a global vision of the subject matter,

the scope of this work is not limited in terms of industrial sectors considered but only in

terms of the type of sources used, i.e. from journal publications from established

databases.

The initial approach to this research was to answer the following questions:

1. What is Six Sigma?

2. What are the applications of the Six Sigma?

3. What are the main enablers and barriers to its application?

4. What are the emerging trends?

The purpose of these questions was to guide the search even if it was expected that

existing literature might not be sufficiently developed to translate each question directly

into a finding.

2.2 Search strategy

The search strategy was developed by first identifying the relevant data sources and

keywords. The databases included Scopus, ABI/Inform, IEEE Xplore and Emerald. The

time frame was chosen initially to include only the literature published between 2004

and 2009, however, as the research progressed, this was extended as a result of cross

citations to include papers from 2000.

The search set out by choosing a set of keywords and possible combinations that could

be significant to Six Sigma. The concept of Six Sigma embraces a very wide range of

aspects and so a considerable number of search strings were deemed necessary.

These captured all the aspects that characterise Six Sigma, such as definition,

methodology, techniques, tools, implementation, enablers and issues. Keywords

4

related to other important concepts to analyse possible connections were also used.

Examples of these include lean, supply chain management, process management and

sustainability.

Table 1 shows the number of items associated with some of the search strings used. It

shows the publications related to the implementation of Six Sigma, the associated tools

and techniques and the DMAIC methodology. Also quite developed in literature is the

topic of “Lean and Six Sigma”. Perhaps surprisingly, the keywords “Six Sigma +

sustainability” only retrieved 12, although the concept of sustainable production was

presented almost 30 years ago (Miron and Skarke, 1981).

Table 1 – Keywords search results

Keywords Journal papers(Scopus+ABI)

S1 Six Sigma + definition 12+14S2 Six Sigma + implementation 114+100S3 DMAIC 83+56S4 DFSS 46+19S5 Six Sigma + Tools OR Techniques 207+145S6 Six Sigma + simulation 30+12S7 Six Sigma + sustainability 7+5S8 Six Sigma + TQM 27+55S9 Six Sigma + Lean 108+123S10 Six Sigma + Supply Chain 18+16

The main exclusion criterion in this search was to take into account only papers

focused primarily on Six Sigma, ignoring consequently the ones that cited it as

methodology used but did not go in depth in the dissertation about it.

2.3 Results and analysis

The search strategy initially identified 210 publications. However, each work was

checked by first reading the abstracts so that those that appeared to be outside the

scope of the review, because of the vagueness and lack of detail for instance, were

excluded. Following the screening, the papers were reduced to 167 as a result from

more thorough examination to derive the main contents. By analysing the authorships

5

of those papers (Figures 1 and 2) it can be seen how the interest is roughly equally

distributed between industry and academia, and how the applications of Six Sigma in

the service sector are becoming more prevalent. After this step, 76 publications were

identified as being available and suitable for the present work and an analysis was

conducted on these particular papers because of the higher level of detail offered

compared to the rest of the papers. The results of these search help provide the

following series of key findings.

Figure 1 – Number of articles and their authorship

Figure 2 – Percentage of articles focused on manufacturing and services

6

3. GENERATION OF KEY FINDINGS

The literature review established seven key findings (topics on which the views of the

authors converged) and two principal issues (topics on which authors had differing

views). This section presents each of them.

3.1 Definition of Six Sigma

From the various definitions found in the reviewed publications, it was possible to

identify at least four streams of thought of Six Sigma.

The first stream defines Six Sigma as a set of statistical tools adopted within the quality

management to construct a framework for process improvement (Goh and Xie, 2004;

McAdam and Evans, 2004). The objective is to enhance the Six Sigma level of

performance measures referred to as the Critical to Quality (CTQ) which reflects the

customer requirements through a group of tools for the analysis of the data. Statistical

tools identify the main quality indicator which is the Parts per Million (PPM) of non-

conforming products (Mitra, 2004). Achieving a Six Sigma level means having a

process that generates outputs with less than 3.4 defective parts per million (Coleman,

2008; Anand et al, 2007). Here, Six Sigma is recognised as a problem solving method

that uses quality and statistical tools for basic process improvements but not

necessarily a comprehensive management system.

The second stream defines Six Sigma as an operational philosophy of management

which can be shared beneficially by customers, shareholders, employees and suppliers

(Chakrabarty and Tan, 2007). Thanks to its flexibility, Six Sigma application is not

limited only to manufacturing but can be extended to the whole supply chain which

include the provision of services. It is, according to Yang et al (2007), useful to enforce

a more disciplined approach towards supply chain projects to define and execute them

more rigorously. Six Sigma is also defined as a multifaceted, customer oriented,

7

structured, systematic, proactive and quantitative philosophical approach for business

improvement to increase quality, speed up the deliveries and reduce costs (Mahanti

and Antony, 2005).

The third stream defines Six Sigma as a business culture. This stream argues that the

success of Six Sigma does not rely only on statistical tools and techniques but also on

the commitment of the top management to guarantee the involvement of the

employees in the organisation. Markarian (2004) considers Six Sigma as a rigorous top

down methodology which demands detailed analysis, fact based decisions and a

control plan to ensure ongoing quality control of a process. This organisational aspect

is also shown in the work of Pheng and Hui (2004), who define Six Sigma as a ‘cultural

and belief’ system which guides the organisation in repositioning itself towards world

class business performance by enhancing factual decision making. Similar definition is

given by Schroeder et al (2008) who consider Six Sigma as an organised structure

using process improvement specialists with the aim of achieving strategic objectives.

The fourth definition refers Six Sigma to as an analysis methodology that uses the

scientific methods. Banuelas and Antony (2004) and Thawani (2004) consider it as a

well structured continuous improvement methodology to reduce process variability and

remove waste within the business processes. Black and Revere (2006) support this by

claiming Six Sigma as a popular and widely used quality improvement methodology.

Kumar et al (2007) argue that Six Sigma ia an extension to quality improvement

initiatives such as the Total Quality Management (TQM) because of the similarities

between the Six Sigma method of Design, Measure, Analyse, Improve, Control

(DMAIC) and the Deming’s PDCA (Plan, Do, Check and Act). Using the DMAIC

method sequentially can help integrate human aspects (culture change, training,

customer focus) and process aspects (process stability and capability, variation

reduction) within the Six Sigma implementation (Antony et al, 2005).

8

Finding 1: Four interpretations of Six Sigma have been identified in the literature as a

set of statistical tools, an operational philosophy of management, a

business culture and an analysis methodology that uses the scientific

methods, although the streams are not mutually exclusive but instead,

overlapping.

3.2 Six Sigma implementation

Al-Mishari & Suliman (2008) suggest three possible ‘on-ramps’ or approaches an

organisation can take to implement Six Sigma. The first is through a business

transformation approach where an organisation undergoes complete change to convert

its traditional method of working in order to regain lost customers or to overcome the

heavy losses. The second is the strategic improvement approach limited to one or two

critical business needs focusing on major opportunities and weaknesses. The third is a

problem-solving approach which focuses only on persistent problems.

In this respect, many of the publications suggest the Design, Measure, Analyse,

Improve, Control (DMAIC) and the Design for Six Sigma (DFSS) methods as the two

most common methodologies to implement Six Sigma, although according to Edgeman

and Dugan (2008), the main objectives of the two techniques are quite different.

While DMAIC is a problem solving method which aims at process improvement, DFSS

is defined by Watson and DeYong (2010) as “a process to define, design and deliver

innovative products provide competitively attractive value to customers in a manner

that achieves the critical-to-quality characteristics for all the significant functions”. It is

therefore clear from this definition that DFSS is used in the context of new product

development that focuses on quality from the very beginning (Edgeman and Dugan,

2008). To this end, Mader (2006) believed that companies with strong market growth

and competitive position will be better-off with DFSS (focusing on product development

9

and innovation), whereas for companies with stagnant market or relatively less

competitive, DMAIC is generally a more favourable choice focusing on cost reduction,

retrenchment or divestiture.

Deploying the two approaches in different parts of the business simultaneously is

possible, even if most of the publications reviewed presented the case studies based

on either of them. As a general trend, many organisations have now extended DMAIC

to include DFSS (Mader, 2006). Possible reason is that many companies typically train

their employees in DMAIC first then expand it to DFSS which is tailored to the context

of new product and/or service development. In this respect, Banuelas and Antony

(2004) stated that in order to achieve the Six Sigma figure of 3.4 parts per million of

defects is to redesign products, key processes and services by means of DFSS. This

argument is, however, debatable as no literature clearly accepts or rejects this

hypothesis. Nonetheless, Edgeman and Dugan (2008) argue that both DMAIC and

DFSS are firmly rooted in the scientific method and are in many ways analogous to the

familiar approaches used either by the hypothesis testing or the iterative experimental

design.

The literature further shows that there are several variations for DMAIC (even if it

remains the most commonly adopted methodology) such as P-DMAIC (Project-

DMAIC), E-DMAIC (Enterprise-DMAIC) and DMAICR (DMAIC Report). The differences

are mostly in terms of the number and type of phases, rather than the tools used.

DMAICR, for instance, adds the final step of “Reporting the benefits of the re-

engineered process” into DMAIC (Senapati, 2004). Numerous variations of DFSS also

exist, for example DMADV (Define Measure Analyse Design Verify), DCOV (Design

Characterise Optimise Verify), IDOV (Identify Design Optimise Validate), ICOV (Identify

Characterise Optimize Verify) and DMADV (Define Measure Analyse Design Verify),

but in this case, there are no significant differences amongst them. The selection of the

10

methodology, in the end, depends on the specific requirements (Chakrabarty and Tan,

2007) and some companies implement Six Sigma not only at the project level but also

at the enterprise level (Ward et al, 2008). In these instances, either P-DMAIC or E-

DMAIC approach is generally used (Breyfogle III, 2008). Watson and DeYong (2010)

provide a comprehensive chronological alternative approaches to DFSS.

Finding 2: Depending on the purpose, there are two principal methodologies in which

Six Sigma can be implemented: DMAIC and DFSS. DMAIC is generally

used for process improvement and DFSS for new development of product

and services. Literature presents many variations of both.

3.3 Tools and techniques of Six Sigma

Many tools and techniques that can be applied to Six Sigma projects are available both

in the literature and public domain, e.g. Halliday (2005). Although most of these tools

are already well known and applied in other contexts, Six Sigma provides a customer

focused, well defined methodology supported by a clear set of comprehensive tools for

process improvement (van Iwaarden et al, 2008). Basic tools of DMAIC, typically used

at the Yellow-Belt level of competence include flowcharts, check sheets, Pareto

diagrams, cause/effect diagrams, scatter diagrams, histograms and Statistical Process

Control (Ferrin et al, 2005). More advanced tools such as regression analysis (e.g. with

indicator variables, curvilinear regression and logistic regression), hypothesis testing,

control charts and Design of Experiments typically feature at the Black-Belt level. This

also means Six Sigma may be viewed as a combination of existing tools and

techniques available well before Motorola developed this approach (van Iwaarden et al,

2008).

Tools are also available in various forms such as models, analysis templates and

procedures (de Koning and de Mast, 2006) and it is this wealth of techniques that

11

complicates the process, making the need of a robust set of what are essential

improvement tools to be used within the DMAIC process more obvious (Brady and

Allen, 2006). One important aspect to consider when embarking any Six Sigma project

is that tools will have to adapt and develop as the project matures. Often, simple tools

are enough to reduce the defects of a complex manufacturing system in the initial

stages (Raja, 2006).

Even though tools and techniques vary, it is essential to apply the right tool in the right

situation in order to achieve successful results. This perhaps justifies why it is a

common practice in the literature to catalogue the main tools within the five phases of

the DMAIC approach. However, there is an absence of standardised decision

procedures to choose the most appropriate tools in a specific context (Hagemeyer et

al., 2006; Kumar et al., 2008a; Williams, 2009; de Koning et al., 2008). Likewise, as put

forward by Brady and Allen (2006), finding literature that provides methods for specific

projects and the associated financial results is often difficult because of the

confidentiality reasons.

Over the years, companies have included numerous tools into the Six Sigma approach

to make them more effective and to eliminate possible gaps after its application. Such

toolsets include statistical and analytical tools both from industrial engineering and

operations research fields (Bunce et al, 2008). In this instance, these tools enrich the

practical and industrial approach with a stronger theoretical basis to achieve a better

equipment and resources utilisation (Maciel Junior et al, 2005).

The tools within the DFSS methodology are usually different from those of the DMAIC.

Chakrabarty and Tan (2007) claim that DFSS typically includes innovation tools such

as the theory of creative problem solving and axiomatic design which DMAIC does not,

although it could.

12

One notable observation during the review was the use of simulation techniques within

the ‘Improve’ phase. Although not part of the keyword search, the use of simulation is

commonly referenced in the papers but does not consistently appear in the tool

categorisation lists. Simulation is one of the tools deserving special mention as an

emerging technique that can play an important role in Six Sigma initiative today and is

considered by some authors, for example McCarthy and Stauffer (2001), to be “vital to

the long-term success of Six Sigma projects”. The evolution of computer hardware has

enabled the use of powerful simulation packages for the Analyse and Improve stages,

as it allows significant savings in the Design of Experiments phase by testing solutions

before implementation (Gladwin, 2003). Simulation has been very successful on its

own for the past twenty years but this tool was not seen as complementary to Six

Sigma and only few articles addressed the combination of such tool and methodology.

This is no longer the case today, and although still few, some authors such as

McCarthy and Stauffer (2001) state in their text that Six Sigma has already delivered

significant results without the benefit of simulation but agree that simulation could make

Six Sigma even more successful in the coming years.

Finding 3: The literature provides a wealth variety of tools and techniques which are

often classified within the DMAIC approach but with little detail on specific

examples of their applications. Basic tools are often sufficient for the initial

improvements of most processes but the simulation techniques open up a

new and promising avenue to enhance the merits already achieved by Six

Sigma.

Issue 1: The variety of tools available sometimes causes confusion as to which

tools work best for specific business requirements. Existing literature also

categorises the Six Sigma tools based under DMAIC, however, alternative

13

approaches such as DFSS, DCOV or DMADV lack this classification of

tools.

3.4 Benefits of Six Sigma

Reduced costs, reduced project time, improved results and improved data integrity are

some of the benefits of Six Sigma suggested by Ferrin et al (2005). In addition, the

literature tends to analyse the techniques used to optimise the process performance.

The approach taken in many cases, e.g. by Lin et al (2008) and Antony et al (2005a), is

to give the solutions and the methods built by Six Sigma to achieve sensible

improvements, providing a learning process for managers in order to take a wide view

of the system and change effectively the business (Thawesaengskulthai and Tannock,

2008). There are many benefits that can be derived from the adoption of Six Sigma. It

could enhance product development cycles and process design, shorting product lead

times by reducing the cycle time of the overall manufacturing process. Six Sigma can

be used to find and eliminate the root causes of the problem, so reducing the variability

in the process in order to prevent defects.

There are also organisational implications. Indeed Six Sigma methodologies provide

guidelines which could help the workers understand how to carry out the job and train

them to solve potential problems. As a consequence, they become more aware of the

production process thereby improving their morale and reducing the human-related

defects (Hong et al, 2007). With respect to the role of Six Sigma in reducing the

defects, it has been demonstrated in several studies that the defect rate per unit (DPU)

is reduced after its implementation in manufacturing systems (Kumar et al, 2006).

The adoption of Six Sigma has improved both the efficiency of the line and production

capability, including minimising waste such as reduced need for inspection, removed

useless components and excessive movements and decreased time for repair (Oke,

14

2007). For this reason, Six Sigma can be used to build predictive models based on

experiences gathered from earlier uncorrected measures to ensure a continuous

improvement of the process (Johnston et al, 2008). In recent years, knowledge

management has contributed to facilitate the implementation of Six Sigma and has

emerged as a source of competitive advantage within the businesses (Gowen III et al,

2008). Six Sigma is also recognised as a strategy that drives the cultural change to

improve profitability of the company increasing the benefits from savings generated

when the defect is detected at a very early stage (Antony et al, 2005a). However, van

Iwaarden et al (2008) state that the approach to Six Sigma varies between

organisations because they integrate different techniques according to their needs, so

there might be disagreement regarding the benefits as they depend on the industry and

even the country where Six Sigma is applied.

Six Sigma also helps improve the relationships outside and within the organisation

(Kumar et al, 2006). It can strengthen the customer loyalty by satisfying their needs

and expectations and it works as a direct link to company’s management which helps

establish a common language from the board to the shop floor.

Finding 4: Six Sigma has many benefits and, unsurprisingly, the most frequently

cited are the reduction and prevention of defects which affect the quality

of both products and processes.

3.5 Six Sigma Adoption

Over time, Six Sigma has developed and undergone significant changes. It initially

applied in the manufacturing sector but has now spanned over service and financial

sectors (Aghili, 2009). Antony (2007) grouped these changes into three generations.

The first generation of Six Sigma (1987-1994) was focused on reduction of defects and

saw success with Motorola. The second generation (1994-2000) was concentrated on

15

cost reduction and was adopted by companies such as General Electric, Du Pont and

Honeywell. The third generation (2000 onwards) is oriented to creating value for the

customers and the enterprise itself, and finds its application within companies like

Posco and Samsung. This is more oriented to service and commercial business

processes including transactional systems quality, which takes into account delivery

times, customer waiting time to receive services, inventory service levels, etc.

Although the application of Six Sigma in service sectors is growing, the majority of the

publications reviewed discuss the implementation and the problems encountered within

the manufacturing sectors. Possible explanation of this is, according to Hensley &

Dobie (2005), is because the service sector is dealing with intangible entities such as

customer service, i.e. providing the assistance necessary to establish good

relationships with them and aiming at an efficient communication to meet their

expectations, where the success is more difficult to quantify. On the contrary, in the

manufacturing sectors where an automatic data collection is used, for example in

assembly lines, measuring the impact of the quality control programme is much easier

to do. Furthermore, large organisations tend to initially introduced Six Sigma in their

manufacturing facilities. Only after enhancing their knowledge about the tools and

techniques to adopt, they gradually spread it to the service operations.

Literature also shows there is a different level of interest shown in the Six Sigma

adoption not only in terms of type of operations (manufacturing or service) but also in

terms of company size. In particular, multinational companies are often reported to

have reaped the full benefits of Six Sigma. However, because of the project-based

approach in DMAIC, Small and Medium Enterprises (SME) should also benefit from it

(Antony et al, 2005a).

16

It also emerged that many large companies, e.g. Xerox, Fidelity Investments, integrate

Six Sigma with other techniques such as Lean (Ranch, 2006; Hensley & Dobie, 2005),

Quality Management System (Morgan & Brennig, 2006), and Kaizen/Continuous

Improvement, e.g. Caterpillar (Haikonen et al, 2004). This shows how the availability of

resources can play an important role in successful adoption of Six Sigma that can be

powerfully integrated other techniques to get optimum benefits out of it (Nonthaleerak,

& Hendry, 2008). Furthermore, Pantano et al (2006) proposed the application of Six

Sigma in a cluster of small companies so that they can share their resources and

achieve the needed level of inputs as possible solution to overcome the difficulties

found in the SMEs.

Finding 5: Six Sigma is very much in use within the manufacturing sector but is

growing in the service sector. More research is required to understand Six

Sigma adoption within the SMEs.

3.6 Enablers of Six Sigma

There is little evidence in the literature to highlight linkage between Six Sigma and

organisation culture despite their combinatorial significance in present day

manufacturing or service organisations (Davison & Shagana, 2007). However, sound

success of it is likely in the event of continuous refinement of culture in organisation

(Kwak & Anbari, 2006). Lee-Mortimer (2007) observed a company wide training to

promote Six Sigma as a relevant tactic to combat initial reluctance towards cultural

change. He also suggested that reducing the levels in organisational structure may

speed up the adoption of Six Sigma culture. Welch (2005) believed that it is necessary

to make Six Sigma a leadership tool for transformation that should permeate into all

levels of businesses. The effort required is to change the approach to the

implementation of Six Sigma projects from merely using a set of tools to the creation of

a culture that should be deeply embedded in every employee (Antony, 2004).

17

Involvement and commitment from top management is the prime enabler in increasing

level of a Six Sigma programme implementation (Chung et al, 2008). Furthermore, in

order to facilitate the communication within the organisation and to support the

implementation process, Information Technology and state-of-the-art Information

Systems infrastructure are fundamental. They continually enable integration of complex

tasks in obtaining feasible quality improvement solutions in a short time frame (Hsieh et

al, 2007). Thanks to an organised and systematic approach, the role of Six Sigma as a

‘managerial tool’ for improving quality and productivity can be extended to a ‘systemic

tool’ for quality and process control (Han et al, 2008).

It is important to note that Six Sigma does not provide a quick and easy solution to all

types of manufacturing problems and the environment in which it is introduced (Lee-

Mortimer, 2006). Furthermore, he also suggested that small and medium enterprises

should gradually adopt Six Sigma as it will help to evenly stretch their resources and

capabilities to get the most out of them. Regardless the size of the company, McAdam

& Laffert (2004) agree that empowerment of people, involvement, motivation, effective

communication, reward and recognition system play a critical role in the success of Six

Sigma implementation. This can be achievable through a transformational leadership,

which is helpful in motivating employees to attain transcendental goals rather than their

own short term interests (Montes & Molina, 2006). This means adapting the strategy

definition, although the above mentioned authors suggest there are few papers in

literature regarding the integration of Six Sigma perspective and practices into the

strategy formulation process even if it inherently is a concern for a successful Six

Sigma initiative.

The linkage between Six Sigma and organisation culture needs to be understood.

Successfully enabling these factors, nurturing quality culture amongst workforce and

taking concern for the issues expressed above, will shape improvements and increase

18

productivity, thereby making Six Sigma more pervasive and indispensable in both

manufacturing and service organisations.

Finding 6: Committed leadership of top management and fully fledged training are

crucial to the success of Six Sigma implementation. Blending IT expertise

with Six Sigma to propel improvements and plausible significant savings

are also important. Human resource functions need good harmonisation

with Six Sigma approach leading to a general involvement within the

organisation.

3.7 Links to other disciplines

The pressure to remain competitive by providing a high quality product to satisfy the

customer requirements has led to a comprehensive analysis of quality, speed and

agility within and outside the company boundaries. Existing literature explicitly identifies

higher customer satisfaction as a significant benefit from the integration of Lean and

Six Sigma concepts (Thomas et al, 2009; Teresko, 2008) but it does not show

consensus about how to create such integration. The majority of the papers present the

DMAIC approach as a roadmap and suggests to call on Lean tools when appropriate to

carry out the two kind of practices in parallel (Thomas et al, 2009; Proudlove et al,

2008; de Koning et al, 2008). In other cases, some authors identified the absence of a

systemic methodology to merge the two concepts resulting in the implementation of

Lean and Six Sigma in sequence (Na ̈slund, 2008; Shah et al, 2008). What is evident

and common, however, is that the amalgamation of the two complementary techniques

has brought significant benefits to the company performance.

Six Sigma has also been applied by Kumar et al (2008b) in the context of supply chain

design. They used DMAIC approach to analyse mitigation of container security risk.

Thanks to the Six Sigma process approach orientation, the supply chain can be

19

monitored and improved using the Six Sigma metrics. Those metrics create a common

denominator (Defect per Unit) for the analysis of all the systems on the same scale,

from products to processes (Dasgupta, 2003; Kumar et al, 2008b).

As previously stated, there is a debate among the authors about the originality of Six

Sigma. Six Sigma offers a common metric to align and evaluate the performance of all

the functions within the organisation and gives a methodology to translate the TQM

philosophy into practices. Six Sigma also keeps the main principles of TQM such as

customer focus (identified as Critical To Quality in the “Define” phase within DMAIC),

employee involvement (Green belts and Black belts team leaders who lead self-

directed work teams are empowered to make changes), continuous improvement (the

“Control” phase within DMAIC), enlightened leadership (represented by the champion

in Six Sigma team) and fact-based decision making (Six Sigma is visibly data oriented)

(Green, 2006; Black and Revere, 2006). There are many benefits applying both Six

Sigma and TQM in complementary because in fact Six Sigma is the extension to TQM,

in which the TQM philosophy is at the core of Six Sigma. As Andersson et al (2006) put

forward, Six Sigma is a structured methodology within the more general framework of

TQM and it provides a series of concepts and tools that support the overall principles

and aims of TQM.

The literature also demonstrates the link between Six Sigma and Kaizen (continuous

improvement) and defines a structure to improve the company performance using the

DMAIC steps and making Six Sigma an ongoing effort (Savolainen & Haikonen, 2007;

Ehie & Sheu, 2005; Murugappan & Keeni, 2003). In fact, Kaizen tools are major tools in

Six Sigma Green belt project.

Not widely documented, however, is the relationship between Six Sigma and the

Process Management. Hammer (2002) recognises the standing-alone as major limit of

20

Six Sigma and states that it should be more aligned with the enterprise and part of the

Process Management in order to identify when the Six Sigma approach is not enough

and a radical re-engineering of the process in needed. Equally rarely reported is the

link between Six Sigma and sustainability. The first authors to study the topic of

sustainability in the production phase were Miron and Skarke (1981). The reason for

this was possibly because the concept of sustainability within Six Sigma is implicitly

contained within the Control phase of the DMAIC. Further research might be needed to

identify possible benefits driven by Six Sigma in this promising field.

Finding 7: Six Sigma is a complementary approach to Lean, an extension to TQM

and is suitable to many applications thanks to its process-oriented view,

brought together in a structured methodology to increase the system

performance and to ensure a continuous improvement culture.

Issue 2: The key areas of connection between Six Sigma and sustainability as well

as the integration between Six Sigma and the Enterprise Process

Management remain relatively unexplored.

4. CONCLUSIONS

In recent years there has been a lot of interest in the application of Six Sigma

principles. Numerous papers have been presented on this subject substantiating the

importance of adopting Six Sigma to improve process performance. This research is

carried out to identify the latest trends, various approaches, tools and techniques,

benefits and combinations of Six Sigma with other concepts by carrying out a

systematic, thematic literature review.

Although there is a considerable amount of publication about Six Sigma and therefore

a lot of different points of view, it is possible to identify four interpretations of Six Sigma:

a set of statistical tools, an operational philosophy of management, a business culture

21

and an analysis methodology that uses the scientific methods, although the streams

are not mutually exclusive but instead, overlapping. The main goals of Six Sigma,

however, remain unchanged, i.e. improving efficiency, profitability and capability in the

process.

There are a large number of tools and techniques within Six Sigma. The variety of

tools, however, often causes confusion as to which tools work best for what

circumstance of the businesses. A systematic way to guide the selection of these of

tools is desirable. Existing literature also traditionally categorises these Six Sigma tools

under DMAIC but classification of tools under other alternative approaches such as

DFSS, DCOV or DMADV is lacking. Possible explanation of this is that all these DFSS

tools are custom-selected for a particular R&D process, industry and use, so a fixed

formulation is not possible beyond a broad categorisation (Watson, 2005).

Another issue, as mentioned before, is to clarify the use of the statistical tools and to

understand how the simulation can help in the proactive analysis of the systems.

Simulation techniques have been identified as one of the promising ones.

The main enabler for Six Sigma implementation is the top management commitment

that can promote an effective companywide training to let all the employees be

involved in the project.

The initial methodology of Six Sigma was focused on process improvement and

accordingly DMAIC approach was universally adopted, but as time progressed, the

need of implementing Six Sigma at design stage of product (or process) was felt crucial

and hence the concept of Design for Six Sigma (DFSS) was developed. Several

slightly different variations of the aforementioned approaches are available in the

literature.

22

Despite the increased number of papers discussing the adoption of Six Sigma in the

service sector in the last few years, the detailed implementation in Small and Medium

Enterprises (SMEs) was not widely reported in the academic literature, with the

exception of e.g. Antony et al (2005a) and Nonthaleerak & Hendry (2008).

The literature also supports the view that by adopting Six Sigma the variability in a

process will be reduced. In addition to the direct savings which are achieved by

improved quality and reduced scrap, the organisation can also be benefited from the

indirect savings such as in lower rework cost, minimum product recalls, low warranty

liabilities, higher customer satisfaction and brand loyalty.

These findings support the view that despite Six Sigma is considered as a fully

developed methodology, further research is needed to establish a more systematic

approach to help companies, especially SMEs, embark on Six Sigma projects.

Although the general approach is quite well known and largely applied in large

manufacturing organisations, further work is required to investigate implementation of

Six Sigma in the service sector as well as in smaller companies.

This paper has extended the work of Brady and Allen (2006). The findings and issues

have provided new insights to take Six Sigma to the next level. This work also

contributes the theoretical platform enabling deeper analyses to be carried out on the

highlighted fields. As Six Sigma continues to develop and evolve, this type of work

should also carry on.

As for the future work, the key findings and issues arising from the evidence gained in

the literature need to be further validated, in particular, confirmation of the possible link

between Six Sigma and other concepts such as sustainability and the emerging

business model of Product Service Systems (PSS) (Baines et al, 2009). How Six

Sigma can be used to facilitate manufacturing organisations to shift from selling

23

product-only to selling integrated product and services, for example, is yet to be

explored. The authors are mindful that Six Sigma principles and theories were not

developed solely in the academic journals, but instead progressed out of the

practitioners. The role of academics in this respect is to underpin these developments

with a theoretical basis.

5. REFERENCES

Aghili, S. (2009), “A Six Sigma Approach to Internal Audits”, Strategic Finance, vol. 90,

no. 8, pp. 38-43

Al-Mishari, S.T. and Suliman, S. (2008), “Integrating Six-Sigma with other reliability

improvement methods in equipment reliability and maintenance applications”,

Journal of Quality in Maintenance Engineering, vol. 14, no. 1, pp. 59-70

Anand, R. B., Shukla, S. K., Ghorpade, A., Tiwari, M. K. and Shankar, R. (2007), “Six

Sigma-based approach to optimise deep drawing operation variables”,

International Journal of Production Research, vol.45, no. 10, pp. 2365-2385

Andersson, R. and Eriksson, H. and Torstensson, H. (2006), “Similarities and

differences between TQM, six sigma and lean”, TQM Magazine, vol. 18, no. 3, pp.

282-296

Antony, J. (2004), "Some pros and cons of six sigma: an academic perspective", TQM

Magazine, vol. 16, no. 4, pp. 303-306

Antony, J. (2007), “Is six sigma a management fad or fact?”, Assembly Automation, vol.

27, no. 1, pp. 17-19

Antony, J., Kumar, M. and Madu, C. N. (2005a), ”Six Sigma in small and medium sized

UK manufacturing enterprises”, International Journal of Quality and Reliability

Management, vol. 22, no. 8, pp. 860-874

Antony, J., Kumar, M. and Tiwari, M. K. (2005b), “An application of Six Sigma

methodology to reduce the engine-overheating problem in an automotive

company”, Proceedings of the Institution of Mechanical Engineers, Part B: Journal

of Engineering Manufacture, vol. 219, no. 8, pp. 633-646

Arnheiter, E.D. and Maleyeff, J. 2005), “The integration of lean management and Six

Sigma”, The TQM Magazine, vol. 17, no. 1, pp. 5-18

24

Baines, T.S., Lightfoot, H.W, Benedettini, O. and Kay, J.M. (2009), “The servitization of

manufacturing: a review of literature and reflection on future challenges”, Journal

of Manufacturing Technology Management, vol. 20, no. 5, pp. 547-567

Banuelas, R. and Antony, J. (2004), “Six Sigma or Design for Six Sigma”, TQM

Magazine, vol. 16, no. 4, pp.250-263

Black, K. and Revere, L. (2006), “Six Sigma arises from the ashes of TQM with a twist”,

International Journal of Health Care Quality Assurance, vol. 19, no. 3, pp. 259-266

Brady, J.E. and Allen, T.T. (2006), "Six Sigma Literature: A Review and Agenda for

Future Research", Quality and Reliability Engineering International, vol. 22, pp.

335-367

Breyfogle III, F. W. (2008), “Better Fostering Innovation: 9 steps that improve lean six

sigma”, Business Performance Management Magazine, vol. 6, no. 3, pp. 16-20

Bunce, M. M., Wang, L. and Bidanda, B. (2008), “Leveraging Six Sigma with industrial

engineering tools ins crateless retort production”, International Journal of

Production Research, vol. 46, no. 23, pp. 6701-6719

Chakrabarty, A. and Tan, K. C. (2007), “The current state of Six Sigma application in

services”, Managing Service Quality, vol. 17, no. 2, pp.194-208

Chung, Y.C., Hsu, Y.W., and Tsai, C.H. (2008), "An empirical study on the correlation

between Critical DFSS success factors, DFSS implementation activity levels and

business competitive advantages in Taiwan's high-tech manufacturers.", Total

Quality Management, vol. 19, no. 6, pp. 595-607

Coleman, S. (2008), “Six Sigma: An opportunity for statistics and for statisticians”,

Significance, vol. 5, issue 2, pp. 94-96

Dasgupta, T. (2003), “Using the six-sigma metric to measure and improve the

performance of a supply chain”, Total Quality Management and Business

Excellence, vol. 14, no. 3, pp. 355-366

Davison, L. and Shaghana, K.A (2007), "The Link between Six Sigma and Quality

Culture: An Empirical Study", Total Quality Management, vol. 18, no. 3, pp. 249-

265

de Koning, H. and de Mast, J. (2006), “A rational reconstruction of Six-Sigma’s

breakthrough cookbook”, International Journal of Quality & Reliability

Management, vol. 23, no. 7, pp.766-787

25

de Koning, H., de Mast, J., Does, R.J.M.M., Vermaat, T. and Simons, S. (2008),

“Generic Lean Six Sigma Project Definitions in Financial Services”, Quality

Management Journal, vol. 15, no. 4, pp. 32-45

Edgeman, R. L. and Dugan, J. P. (2008), “Six Sigma from products to pollution to

people”, Total Quality Management, vol. 19, no. 1-2, pp. 1-9

Ehie, I. and Sheu, C. (2005), “Integrating six sigma and theory of constraints for

continuous improvement: A case study”, Journal of Manufacturing Technology

Management, vol. 16, no. 5, pp. 542-553

Ferrin, D., Miller, M. and Muthler, D. (2005), “Lean sigma and simulation, so what’s the

correlation? V2”, in: Proceedings of the 2005 Winter Simulation Conference, 4-7

December 2005, Orlando, Florida, pp. 2011-2015

Furterer, S. and Elshennawy, A.K. (2005) “Implementation of TQM and lean Six Sigma

tools in local government: a framework and a case study”, Total Quality

Management & Business Excellence, vol. 16, issue 10, pp. 1179 - 1191

Gladwin, B. (2003), “Six Sigma & Simulation”, Promodel White Paper,

http://www.hearne.com.au/attachments/White%20Paper_Simulation%20Enhances

%20Six%20Sigma.pdf, last accessed 2 June 2010

Goh, T. N. and Xie, M. (2004), “Improving on the Six Sigma paradigm”, TQM

magazine, vol. 16, no. 4, pp. 235-240

Gowen III, C. R., Stock, G. N. And McFadden, K. L. (2008), “Simultaneous

implementation of Six Sigma and knowledge management in hospitals”,

International Journal of Production Research, vol. 46, no. 23, pp. 6781-6795

Green, F. B. (2006), “Six-sigma and the revival of TQM”, Total Quality Management

and Business Excellence, vol. 17, no. 10, pp. 1281-1286

Hagemeyer, C., Gershenson, J. K. and Johnson, D. M. (2006), “Classification and

application of problem solving quality tools”, TQM Magazine, vol. 18, no. 5, pp.

455-483

Haikonen, A., Savolainen, T. and Järvinen, P. (2004), “Exploring Six Sigma and CI

capability development: Preliminary case study findings on management role”,

Journal of Manufacturing Technology Management, vol. 15, no. 4, pp. 369-378

Halliday, S. (2005), “Application of Tools in Six Sigma”,

http://www.wdpc.co.uk/articles/tools6sig.pdf, last accessed 25 November 2009.

26

Hammer, M. (2002), “Process management and the future of six sigma”, MIT Sloan

Management Review, vol. 43, no. 2, pp. 26-32

Han, H.S., Chae, M.J., Im, K.S. and Ryu, H.D. (2008), "Six Sigma-Based Approach to

Improve Performance in Construction Operations", Journal of Management in

Engineering, vol. 24, no. 1, pp. 21-31

Hensley, R. L. and Dobie, K. (2005), “Assessing readiness for Six Sigma in a service

setting”, Managing Service Quality, vol. 15, no. 1, pp. 82-101

Hong, K., Nagarajah, R., Iovenitti, P., and Dunn, M. (2007), “A Sociotechnical

Approach to Achieve Zero Defect Manufacturing of Complex Manual Assemblies”,

Human Factors and Ergonomics in Manufacturing, vol. 17, no. 2, pp. 137–148

Hsieh, C.T., Lin, B. and Manduca, B. (2007), "Information Technology and Six Sigma

Implementation", Journal of Computer Information Systems, vol. 47, no. 4, pp. 1-10

Johnston, A. B., Maguire, L. P., McGinnity, T. M. (2008), “Disentangling causal

relationships of a manufacturing process using genetic algorithms and six-sigma

techniques”, International Journal of Production Research, vol.46, no. 22, pp.

6251-6268

Kumar, M., Antony, J., Antony, F. J. and Madu, C. N. (2006), “Winning Customer

Loyalty in an Automotive Company through Six Sigma: a Case Study”, Quality

Reliability Engineering International, vol. 23, pp. 849–866

Kumar, M., Antony, J., Madu, C. N., Montgomery, D. C., and Park, S. H. (2008),

“Common myths of Six Sigma demystified”, International Journal of Quality and

Reliability Management, vol. 25, no. 8, pp. 878-895

Kumar, S., Jensen, H. and Menge, H. (2008), “Analyzing Mitigation of Container

Security Risk Using Six Sigma DMAIC Approach in Supply Chain Design”,

Transportation Journal, vol. 47, no. 2, pp. 54-67

Kumar, U. D., Nowicki, D., Ramirez-Marquez, J. R. and Verma, D. (2007), “On the

optimal selection of process alternatives in a Six Sigma implementation”,

International Journal of Production Economics, no. 111, pp. 456-467

Kumar, S. and Bauer, K.F. (2010) “Exploring the Use of Lean Thinking and Six Sigma

in Public Housing Authorities”, Quality Management Journal, vol. 17, no. 1

Kwak, Y.H. and Anbari, F.T. (2006), "Benefits, Obstacles and future of Six Sigma

approach", Technovation, vol. 26, no. 5-6, pp. 708-715

27

Lee-Mortimer, A. (2006), "Six Sigma: a vita improvement approach when applied to the

right problems, in the right environment", Assembly Automation, vol. 26, no. 1, pp.

10-17

Lee-Mortimer, A. (2007), "Leading UK manufacturer probes the potential of Six Sigma",

Assembly Automation, vol. 27, no. 4, pp. 302-308

Lin, L. C., Li, T. S. and Kiang, J. P. (2008), “A Continual Improvement Framework with

Integration of CMMI and Six-Sigma Model for Auto Industry”, Quality and Reliability

Engineering International, vol. 25, issue 5, pp. 551 - 569

Maciel Junior, H., Batista Turrioni, J., Cesar Rosati, A., Garcia Neto, D., Kenji Goto, F.,

Fujioka Mologni, J., Machado Fernandes, M. (2008), “Application of Design for Six

Sigma (DFSS) on an Automotive Technology Development Process”, SAE

Technical paper series

Mader, D. P (2006), “Deploying the 'D' in DFSS”, Quality Progress, vol. 39, no. 7, pp.

73-74

Mahanti, R. and Antony, J. (2005),”Confluence of Six Sigma, Simulation and Software

development”, Managerial Auditing Journal, vol. 20, no.7, pp.739-762

Markarian, J. (2004),”What is Six Sigma?”, Reinforced Plastics July-Aug 2004, pp. 46-

49

Mcadam, R. and Evans, A. (2004), “Challenges to Six Sigma in a high technology

mass manufacturing environments”, Total Quality Management, vol. 15, no. 5-6,

pp. 699-706

McAdam, R. and Laffert, B. (2004), "A multilevel case study critique of six sigma:

Statistical control or strategic change?", International Journal of Operations and

Production Management, vol. 24, no. 5-6, pp. 530-549

McCarthy, B. and Stauffer, R. (2001), “Enhancing six sigma through simulation with

iGrafx process for six sigma”, in: Proceedings of the 2001 Winter Simulation

Conference, vol. 2, 9-12 December 2001, Arlington, USA, p. 1241-1247

Miron, J.R. and Skarke, P. (1981), “Non-price information and price sustainability in the

Koopmanns-Beckmann problem”, Journal of Regional Science, vol.21, no.1,

pp.117-122

Mitra, A. (2004),”Six Sigma Education: a critical role for academia”, TQM magazine,

vol. 16, no. 4, pp.293-302

28

Montes, F.J.L. and Molina, L.M. (2006), "Six Sigma and Management Theory:

Processes, Content and Effectiveness", Total Quality Management, vol. 17, no. 4,

pp. 485-506

Morgan, J. and Brennig, M. J. (2006), “Six Sigma and the Future of Quality”,

Management Services, vol. 50, no. 2, pp. 46-47

Murugappan, M. and Keeny, G., (2003), “Blending CMM and Six Sigma to meet

business goals”, IEEE Software, vol. 20, no.2, pp.42-48

Näslund, D. (2008), “Lean, six sigma and lean sigma: Fads or real process

improvement methods?”, Business Process Management Journal, vol. 14, no. 3,

pp. 269-287

Nonthaleerak, P. and Hendry, L. (2008),”Exploring the Six Sigma phenomenon using

multiple case study evidence”, International Journal of Operations and Production

management, vol. 28, no. 3, pp.279-303

Oke, S. A. (2007), “Six Sigma: A literature Review”, South African Journal of Industrial

Engineering, vol. 18, no. 2, pp. 109-129

Pantano, V., Kane, P. O. and Smith, K. (2006), “Cluster-Based Six Sigma Deployment

in Small and Medium Sized Enterprises”, Management of Innovation and

Technology, vol. 2, pp. 788-792

Patel, S.C. and Zu, X. (2009), “E-government application development using the Six

Sigma approach”, Electronic Government, an International Journal, vol. 6, no. 3,

pp. 295 - 306

Pheng, L. S. and Hui, M. S. (2004), “Implementing and Applying Six Sigma in

Construction”, Journal of Construction Engineering and Management, vol. 130, no.

4, pp. 482-489

Proudlove, N. and Moxham, C. and Boaden, R. (2008), “Lessons for lean in healthcare

from using six sigma in the NHS”, Public Money and Management, vol. 28, no. 1,

pp. 27-34

Raja, A. (2006), “Simple Tools for Complex Systems”, Quality Progress, vol. 39, no. 6,

pp. 40-44

Ranch, H. (2006), “Xerox Find the Right Tool for Tracking Continuous Improvement”,

Manufacturing Business Technology, vol. 24, no. 2, pp. 42-45

29

Savolainen, T. and Haikonen, A. (2007), "Dynamics of organizational learning and

continuous improvement in six sigma implementation", TQM Magazine, vol. 19, no.

1, pp. 6-17

Schroeder, R. G., Linderman, K., Liedtke, C. and Choo, A. S. (2008),”Six Sigma:

Definition and Underlying theory”, Journal of operations management, no. 26, pp.

536-554

Sehwail, L. and DeYong, C. (2003), “Six Sigma in health care”, Leadership in Health

Services, vol. 16, no. 4, pp. 1-5

Senapati, N. R. (2004), “Quality and Reliability Corner: Six Sigma: myths and realities”,

International Journal of Quality and Reliability Management, vol. 21, no. 6/7, pp.

683-690

Shah, R. and Chandrasekaran, A. and Linderman, K. (2008), “In pursuit of

implementation patterns: The context of Lean and Six Sigma”, International

Journal of Production Research, vol. 46, no. 23, pp. 6679-6699

Teresko, J. (2008), “How to organize for lean/Six Sigma”, Industry Week, vol. 257, no.

11, pp. 38-41

Thawani, S. (2004), “Six Sigma – strategy for organizational excellence”, Total Quality

Management, vol. 15, no. 5-6, pp.655-664

Thawesaengskulthai, N. and Tannock, J.D.T. (2008), “A Decision Aid for Selecting

Improvement Methodologies”, International Journal of Production Research, vol.

46, no. 23, pp. 6721-6737

Thomas, A. and Barton, R. and Chuke-Okafor, C. (2009), “Applying lean six sigma in a

small engineering company- A model for change”, Journal of Manufacturing

Technology Management, vol. 20, no. 1, pp. 113-129

van den Heuvel, J., Does, R.J.M.M. and Verver, J.P.S. (2005), “Six Sigma in

healthcare: lessons learned from a hospital”, International Journal of Six Sigma

and Competitive Advantage, vol. 1, no. 4, pp. 380 - 388

van Iwaarden, J., van Der Wiele, T., Dale, B., Williams, R. and Bertsch, B. (2008), “The

Six Sigma improvement approach: a transnational comparison”, International

Journal of Production Research, vol. 46, no. 23, pp. 6739-6758

Ward, S.W, Poling, S.R. and Clipp, P. (2008), “Selecting Successful Six Sigma

Projects”, Quality, vol. 47, no. 10, pp. 50-51

30

Watson, G.H. (2005), “Design for Six Sigma: Innovation for Enhanced

Competitiveness”, Goal/QPC

Watson, G.H. and DeYong, C.F. (2010), “Design for Six Sigma: caveat emptor”,

International Journal of Lean Six Sigma, vol. 1, No. 1, pp. 66-84

Wei, C., Sheen, G., Tai, C. and Lee, K. (2010), “Using Six Sigma to improve

replenishment process in a direct selling company, Supply Chain Management,

vol. 15, issue 1, pp. 3-9

Welch, J. (2005), “Six Sigma Leaders”, Quality, vol. 44, no. 3, pp. 80-80

William, S. (2009), “The Lean Toolkit, Part I”, CiruiTree, vol. 22, no. 2, pp. 36

Yang, H.M., Choi, B.S., Park, H.J., Suh, M.S. and Chae, B. (2007), “Supply chain

management Six Sigma: a management innovation methodology at the Samsung

Group”, Supply Chain Management: An International Journal, vol. 12, no. 2, pp.

88-95