Critical review of literature on Lean Six Sigma methodology

Abstract

Purpose

This paper aims to develop an initial understanding of the Lean Six Sigma methodology since its inception and examine the few Lean Six Sigma dimensions as a research domain through a critical review of the literature.

Design/methodology/approach

The paper is structured in two-part. The first part of the paper attempts to dwell on the evolution of the Lean Philosophy and Six Sigma methodology individually and the emergence of Lean Six Sigma methodology, covered under the Lean Six Sigma: a historical outline section. The second part of the study examines the dimensions associated with Lean Six Sigma such as frameworks, critical success factors, critical failure factors, type of industry, performance metric, year, publisher and journal, based on a total of 223 articles published in 72 reputed journals from the year 2000 to 2019 as a literature review.

Findings

The adoption of Lean Six Sigma, as a continuous improvement methodology, has grown enormously in the manufacturing and few service sectors such as health care and higher education during the past decade. The study revealed that researchers came out with conceptual frameworks for the implementation of Lean Six Sigma, whereas the validation through case studies seems to be lacking. The integration of Lean Six Sigma and other approaches with a focus on sustainability and the environment has emerged as a research field. A few of the most common critical success and failure factors were identified from the articles studied during the study.

Research limitations/implications

This paper may not have included some of the studies due to the inaccessibility and selection criteria followed for the study.

Originality/value

This paper will provide an initial introduction on Lean, Six Sigma and Lean Six Sigma and research insights Lean Six Sigma to beginners such as students, researchers and entry-level professionals.

Citation

Patel, A.S. and Patel, K.M. (2021), "Critical review of literature on Lean Six Sigma methodology", International Journal of Lean Six Sigma, Vol. 12 No. 3, pp. 627-674. https://doi.org/10.1108/IJLSS-04-2020-0043

1. Introduction

Many countries worldwide experienced the effects of globalization post Second World War and continued to experience in the 21st century. Due to global competition and rapid development in technology, organizations are experiencing some challenges as innovative and value-enhanced products, wide customer expectations, shorter product development cycles, lowest cost, etc (Bhamu and Sangwan, 2014). Quality, as a value proposition, becomes one of the key ingredients not only in product/service but also in processes. Organizations evolved and developed numerous tools and techniques during the past century as part of the improvement process, resulting in various methodologies/strategies.

Some of the philosophies adopted in different parts of the world were are Plan-Do-Check-Act cycle (Deming, 1986), company-wide quality control (Ishikawa, 1984), Toyota Production System (Ohno, 1988), Six Sigma (Harry, 1998), Lean manufacturing (Womack et al., 1990), total productive maintenance (Nakajima, 1989), total quality management (Feigenbaum, 1991), etc. These are also termed as “quality improvement (QI)” or “continuous improvement (CI)” strategy. According to the Wheeler and Poling (1998), QI/CI be termed as an approach to address the issues with logical and critical thinking, prompt and timely adoption of improvements, and then the use of process behavior charts to maintain the gains (Wheeler and Poling, 1998).

In today’s competitive world, enhancing the quality of the products and processes through continuous improvements is one of the prime objectives for any organization (Thomas et al., 2009). With a focus on customer delight, profitability and reduced cost, “quality” emerged as a central point for the organizations (Sunder, 2016a). As a continuous improvement approach, the lean concept originated from the TPS, focusing on doing more with less (Prasad et al., 2016). On the other hand, the Six Sigma approach initiated, aiming to reduce variations in the process at Motorola and resulted in dramatic improvement (Kuvvetli et al., 2016). Since the inception of Lean and Six Sigma, the number of the organizations adopted Lean and Six Sigma individually during the last 20 years of the 20th century and successfully achieved the improvements in the organizations and realized a positive impact on the firm’s performance (Antony et al., 2017; Sahoo and Yadav, 2018). Few of the organizations benefited adopting Lean and Six Sigma are General Electric, Bank of America, American Express, Citigroup, JP Morgan Chase, Du Pont, Posco, Samsung, Ford, TX Instruments, Allied Signal (or Honeywell today), Kodak, Sony, US Military, General Motors, Chrysler and many more (Antony, 2007; Antony et al., 2017; Antony and Banuelas, 2002; Heckl et al., 2010; Henderson and Evans, 2000; Holweg, 2007; Snee, 2005; Snee and Hoerl, 2005). Ozcelik (2010) reported that US service organizations had improved their service quality by the implementation of Six Sigma. Lean and Six Sigma were emerged during the last half of the 20th century and were the field of investigation for the researchers and practitioners. Both approaches were widely adopted in different organizations resulted in enhancement in performance. However, at the beginning of the 21st century, Lean Six Sigma methodology turned up as a methodology for continuous improvement, got the attention of academicians, researchers and practitioners, and widely adopted in organizations (Snee, 2010). Lean Six Sigma is reported as a fine blend of Lean and Six Sigma and complementary. (Rodgers et al., 2019; Sunder, 2016b; Yadav et al., 2018a). According to few researchers, Lean Six Sigma helps to reduce non-value-added activities, wastes, defects and nonconformities encountered during various processes, addresses the issues related to waste and process flow with a focus to reduce the variation in product and process as well (Bhat et al., 2014; Drohomeretski et al., 2014; Yadav and Desai, 2016). Therefore, the objectives of this study are:

• to learn the evolution of Lean Six Sigma methodology; and

• to explore the current state of affairs from the research perspective in the domain of Lean Six Sigma from the existing literature.

The part of the current study focuses on the questions associated with Lean Six Sigma, i.e. What, Why, When, Where, Whom and How – Lean Six Sigma from the literature. While the other part of the paper explores the dimensions such as frameworks/models for Lean, Six Sigma and Lean Six Sigma, success and failure factors in the implementation, benefits achieved, and its applications in different industrial sectors from the literature.

This paper is organized into six different sections. Section 1 introduces the Lean Six Sigma methodology. Section 2 explains the methodology adopted for the preparation of this article. Section 3 provides a brief summary of the existing reviews on Lean Six Sigma. Section 4 highlights the fundamental aspects of Lean Six Sigma from the historical development perspective. Section 5 discusses the literature analysis of different dimensions of Lean Six Sigma methodology and the research work so far done in the field as a part of the literature review. Section 6 summarizes the findings, gaps and future directions as a concluding remark. This study will provide a detailed outline of Lean Six Sigma, including the research aspects, which may help beginners, researchers and working professionals.

2. Methodology

This review article focuses on building through the understanding of Lean, Six Sigma and Lean Six Sigma methodology and research trends by examining the research articles. The review approach states the selection process of the articles, keywords and criteria based on which the articles were selected. The articles reviewed as a part of the literature review of the current study were from 2000–2019 to understand the evolution of Lean Six Sigma methodology and the associated research aspects during this period. The well-known databases such as Elsevier, Emerald, Taylor and Francis, Springer, Inderscience, Wiley and SAGE were searched with keywords as “Lean,” “Six Sigma” and “Lean Six Sigma” in title. Out of the searched articles, only SCOPUS indexed 762 articles were considered for the study. The articles thus selected were further scrutinized based on the sets of the inclusion and exclusion criteria. The articles published in peer-reviewed academic journals and published in the English language, as English is the primary medium for communication globally, were included for the study. The articles such as editorial notes, reports, preface, thesis, conference articles and working papers were excluded from the study. This scrutiny reduced the number of articles to 395. After this scrutiny, the abstracts of the collected articles further investigated for Lean Six Sigma implementation framework, success and failure factors, and case studies on Lean Six Sigma. This filtered the number of articles to 223 articles from 72 journals, which are thoroughly examined based on the identified parameters under the literature review part. In addition to the literature review part, the relevant references reviewed including resources such as books, relevant articles from conference proceedings, web-based articles and appropriately added in the historical outline of Lean Six Sigma under Section 4. The authors agree that few of the articles may have missed due to certain constraints while preparing this paper because many research articles have been published. The methodology followed for the study is shown in Figure 1.

3. Overview of existing reviews on Lean Six Sigma

While conducting this study from the selected articles, the authors came across ten existing review articles on Lean Six Sigma. These articles were studied to learn the focus and attributes considered. A list of these review articles with its brief description is summarized in Table 1. From the study, it appeared that the existing review articles focused on the application of Lean Six Sigma in both manufacturing and service industries. Few of the authors focused on frameworks, success factors and failure factors to implement Lean Six Sigma. The majority of the articles were published before the period of 2015. Therefore, an attempt is made to understand the Lean Six Sigma addressing answers to the fundamental questions such as What, Why, When, Where, Whom and How as a part of the historical outline section. In addition, the literature review was also carried out to understand the research domain of Lean Six Sigma covering publications between the years 2000 to 2019. Further, this article will provide an initial introduction to Lean, Six Sigma and Lean Six Sigma. It also discusses research insights in the field of Lean Six Sigma to the readers and future scope.

4. Lean Six Sigma: a historical outline

With a focus to have a broader perspective on Lean Six Sigma, this section describes the historical developments taken place in the field of Lean Six Sigma. An attempt is made to answers some of the questions such as What, Why, When, For Whom and How associated with the Lean Six Sigma. Therefore, this part provides theoretical knowledge in the domain of Lean Six Sigma, which can help researchers and entry-level professionals.

4.1 What is Lean Six Sigma?

4.1.1 Lean Philosophy.

After reviewing Henry Ford’s mass production approach and due to the emergence of post-Second World War constraints, Eiji Toyoda and Ohno decided to develop an independent approach as the mass production would not be suitable in Japan (Tohidi and KhedriLiraviasl, 2012). Ohno, along with Shingo, developed Toyota Production System (TPS) with a primary focus to thoroughly reduce the non-value-added wastes and thereby increase the production efficiency. According to Ohno, eliminating waste must be a business’s first objective (Ohno, 1988). The genesis of the TPS was with the focus to eliminate the Muda (waste), Mura (unevenness) and Muri (overburden) (Liker, 2004) [Muda, Mura and Muri - Japanese words]. The two pillars of the house of TPS are jidoka and just-in-time (Liker and Convis, 2011). According to Ohno (1988), overproduction, waiting, transportation, processing itself, inventory, movement and making defective parts were identified as waste. Until the oil crisis in the 1970s, TPS could not receive any attention globally. However, researchers at Massachusetts Institute of Technology, under the International Motor Vehicle Program, studied the manufacturing practices at the assembly level in automobile manufacturing companies, including the Toyota Production System (Bhasin and Burcher, 2006). It was Krafcik (1988), who first coined the word ‘lean’ in his article “Triumph of the lean production system” primarily based on the study of Toyota Production System. Though the TPS caught the attention of the world, it became famous as “lean manufacturing” or “lean production” through the book titled “The Machine that Changed World” by Womack et al. (1990). It was stated that Lean as a “dynamic process of change, driven by a set of principles and best practices aimed at continuous improvement” (Womack et al., 1990). Womack and Jones (1996) explained the five key principles of lean philosophy as “value” from a customer perspective, identification of “value stream,” make it “flow,” establish the “pull” and striving for “perfection.”

According to different researchers, Lean as a philosophy focuses “on eliminating the waste throughout the value stream” (Liker, 1997; Seth and Gupta, 2005; Shah and Ward, 2007), “to reduce processing time and delivery time” (Liker, 1997; Negrão et al., 2017; Staats et al., 2011), “achieve highest product quality at the lowest cost” (Negrão et al., 2017; Reosekar, 2011), and “to reduce or minimize the production system wastes which result in better production system performance and increased value to the customer through higher customer satisfaction in terms of product or service quality and variety” (Thanki and Thakkar, 2011).

4.1.2 Six Sigma methodology.

Motorola, one of the US electronic product manufacturers, realized, accepted the fact about low-quality products, and decided to improve the product quality and achieve tenfold achievement in performance. In his report, Smith found an interesting correlation between poor performance of product and defects occurred in the form of rework during the manufacturing process (Process Quality Associates Inc, 1996). Smith and Harry understood the problem and attempted to find the solutions. They came with the concept of “logic filter,” which finally resulted in the form of a four-stage problem-solving approach: measure, analyze, improve ad control (MAIC) (Brady and Allen, 2006; Desai et al., 2012). This problem-solving approach was known as the Six Sigma program. Due to the Six Sigma programs, Motorola saved more than $16 billion (Brue, 2015). In 1988, Motorola awarded the inaugural Malcolm Baldrige National Quality Award (MBNQA) for its six-sigma program (Bhote, 1989; Gowen et al., 2008). Later, Honeywell and Allied Signal, General Electric and others adopted the Six Sigma program. Based on their experiences to enhance clarity on the problem, General Electric added Define (“D”) stage in the four-stage problem solving, leading to Define, Measure, Analyze, Improve ad Control (DMAIC), i.e. Six Sigma methodology (Hoerl, 2001). In the 1990s, due to Welch's efforts at General Electric, the methodology was treated with more importance and widely adopted (Hahn et al., 2000). Hence, Six Sigma methodology evolved, keeping the primary focus to enhance customer satisfaction by reducing the variability and/or defects.

Sigma (Greek letter – ‘σ’) used to specify the variation (distribution spread) about average (mean) for a set of data. (Zare Mehrjerdi, 2011). Six Sigma is often referred to as a metric, a methodology and a management system. As a metric, Sigma quantifies the measure of performance, which describes how well a process meets requirements. According to the Gaussian distribution, the data set within plus and minus three sigma limit covers 99.73% area covered under normal distribution, i.e. the probability of 2,700 data set (defectives) per million would fall outside three sigma limit assuming the process is centered, whereas in six sigma limit it is 0.002 defectives per million. Motorola considered a shift in the mean by plus and minus 1.5 sigma in their Six Sigma program, arrived at 3.4 defectives per million opportunities (Emil et al., 2010). Therefore, the statistical inference of the lower Sigma level in Six Sigma indicates the more variation about the mean, whereas a higher level of Sigma indicates lower variation.

According to few researchers, Six Sigma as a program focuses “to the near elimination of defects from every product, process and transactions” (Tomkins, 1997), “to accelerate improvement in product, process and service quality by relentlessly focusing on reducing variation and eliminating waste” (Antony and Banuelas, 2002), “to reduce variation, which focuses on continuous and breakthrough improvements” (Andersson et al., 2006) and “to improve business performance, with an emphasis on the voice of the customer and using statistical analysis tools” (Zhan and Ding, 2016).

Antony (2007) and Montgomery and Woodall (2008) described the developments in the implementation of Six Sigma since its inception as three generations. The first generation (1987–1994) focused on reduction in variation and defects in the manufacturing sector, whereas the second generation (1994–2000) focused on improving the business performance through cost reduction and enhanced product design, with an additional focus on the creation of value for not only within an organization but also for its stakeholders treated as the third generation (2000 onwards). Further, they added the implementation of Six Sigma at Motorola, General Electric, Du Pont and Honeywell and Caterpillar, Posco, Samsung and Bank of America as the examples of first, second and third generations.

4.1.3 Lean Six Sigma.

Since the independent origin of Lean Philosophy and Six Sigma, the companies had adopted both the approaches for many years to achieve continuous improvement in the different business environments (Lee and Wei, 2010; Walter and Paladini, 2019). Though both the approaches evolved primarily in the manufacturing domain, the applications in other sectors such as service organizations (Laureani and Antony, 2018; Shah and Ward, 2003; Snee and Hoerl, 2005) and public sectors (Antony et al., 2017a; Prashar, 2016) are reported.

Lean Philosophy aims to produce the products at the highest quality at the lowest cost and in the shortest time (Antony et al., 2017). However, it neither brings process under statistical control (George, 2003). Similarly, the Six Sigma program aims to reduce the defects using statistical tools; Jack welch noticed variations in delivery time and identified variation as evil. Further, George (2002) added time as an improvement metric and realized that Six Sigma does not focus on time. According to Park (2003), Lean Philosophy restructures the manufacturing processes to reduces wasteful activities and variation, while Six Sigma mainly focuses on reducing the variation in the process and/or part. Similarly, according to Corbett (2011), deploying Six Sigma in isolation cannot remove all types of waste from the process, whereas Lean Philosophy in isolation cannot control the process statistically and remove variation from the process. Pillai et al. (2012) correlated lean as a change force while six Sigma as a continuity force. According to Sunder (2016b), Lean Six Sigma provides a wide range of tools set to enhance the performance of the processes and to bring down costs for the organization. Therefore, during the last fifteen years, researchers attempted the simultaneous adoption of both the approaches over individual one, which became more popular and emerged as a tool for operational excellence with enhanced performance in different aspects (Salah et al., 2010; Zhan and Ding, 2016).

The literature study revealed that the maiden attempt of integration of Lean and Six Sigma reported in George Group at the USA in 1986 (Albliwi et al., 2014; Chakravorty and Shah, 2012; Salah et al., 2010; Svensson et al., 2015; Vinodh et al., 2014). Though the word “Lean Six Sigma” was used to represent a system that combines both lean and Six Sigma in 2000 by Sheridan (2000), Lean Six Sigma became more popular due to the publications of M. L. George (Byrne et al., 2007; George, 2002). Kroslid (2001) discussed the possibility of a merger between Lean and Six Sigma to achieve world-class performance.

Some of the definitions of Lean Six Sigma are as follows. Lean Six Sigma as “a methodology that maximizes shareholder value by achieving the fastest rate of improvement in customer satisfaction, cost, quality, process speed and invested capital” (George, 2002), “a business strategy in which the focus is to improve the bottom line and increase customer satisfaction” (Taghizadegan, 2006) and “a business strategy and methodology that increases process performance resulting in enhanced customer satisfaction and improved bottom-line results” (Snee, 2010). Lean Sigma integrates both the variability reduction waste and non-value added elimination tools and techniques for facilitating monetary savings to the organization” (Vinodh et al., 2014).

Lean Six Sigma is an organized strategy from a business perspective that enables industries to effectively recognize the customer desires, eliminates the variability within the production, and reduces all non-value-added activities (Singh and Rathi, 2018).

According to Munro (2009), “Lean Six Sigma is not about working harder; it is about working smarter.”

According to different researchers, Lean Six Sigma is identified as quality excellence methodology (Sunder and Antony, 2018), a tool for operational excellence (Albliwi et al., 2015; Prasanna and Vinodh, 2013)(Albliwi et al., 2015), a majestic process improvement methodology (Sunder, 2016c), system (Maleyeff et al., 2012), a business process improvement strategy (Antony et al., 2012), latest generation of improvement approach (Snee, 2010), strategic deployment approach and belief system (Caldwell et al., 2009), business improvement technique (Spector, 2006) and cost reduction mechanism (Jayaraman et al., 2012).

4.2 Why Lean Six Sigma?

The previous part summarised the evolution of two different strategies and the birth of Lean Six Sigma methodology as an introductory remark. This section elaborates on the reasons for the adoption of Lean Six Sigma as a strategy by organizations.

• Organizations worldwide faced intense global competition in the past and present due to policies such as liberalization, privatization and globalization. Therefore, organizations are forced to reduce operational costs through process optimization. Toyota Corporation did such transformations through the TPS. The organizations, continuously forced to improve with the focus on quality, cost, delivery and flexibility as strategic priorities (Antony et al., 2006) and sustain the business (Chakrabarty and Chuan, 2009).

• The world had seen remarkable technological innovations, even faster than ever before, during the past 40 years. Such technological innovations had resulted in new product development. Significantly, the impact of developments in the field of information technology leads to improvement in processes.

• In the recent past, the global market had experienced a transformation from a producer-driven market to a customer-driven market. The preposition “customer satisfaction” changed to “customer delight” meant as providing the values beyond customer expectations. In general, the customer wants quality products at low cost with on-time delivery. The voice of customer in Lean Six Sigma provides the view of customer’s needs, as a part of the Lean Six Sigma project (George et al., 2004).

• In a recent research study, Rodgers et al. (2019) established that Lean Six Sigma evolved as a methodology and stronger when deployed together instead of individual. Further, the integration of different approaches and concepts with the Lean Six Sigma methodology can result in incremental effects that lead to better outcomes. The studies showed integration of Lean Six Sigma with other approaches such as quality management system, energy management system, environment and sustainable concepts, data science and data mining, agile, artificial intelligence, theory of realistic evaluation and many more for different application areas (Black, 2009; Karthi et al., 2011; Rodgers et al., 2019).

• Design for Six Sigma (DFSS) is a strategy used by organizations to improve the design of products and services, particularly at the new product development stage from scratch. Through this, the project team interprets and design the functionality of customer requirements by optimizing both customer needs and organizational objectives. It involves define-measure-improve-design-verify (acronym as DMADV) (Kumar, 2008). Innovations in products and processes are achieved using Lean Six Sigma throughout an organization (Byrne et al., 2007).

• Arnheiter and Maleyeff (2005) reported the misconceptions about Lean and Six Sigma as lean means layoffs, lean only works in Japan, lean works for manufacturing or within specific environments only, Six Sigma pushed by the consultants and Six Sigma is a quality only program. Further, they justified the integration of the key principles of both approaches as Lean Six Sigma leads to a competitive advantage from the viewpoint of both the customers and the producers.

• Lean Six Sigma is widely used by several organizations worldwide, not only in the manufacturing sector but also in the service sector (Alhuraish et al., 2017). Amongst the all available continuous improvement strategies, the widely used continuous improvement strategy is Lean Six Sigma (Arcidiacono et al., 2016; Gupta et al., 2018).

• The private sector organizations are very well ahead in the adoption of Lean Six Sigma in comparison to public sector organizations. However, the application of Lean Six Sigma has grown in public sector organizations such as healthcare, education, government and police in the recent past (Rodgers et al., 2019). Antony et al. (2017b) suggested possible scope of applications of Lean Six Sigma in public sectors with minimizing the operational cost, adding values to customer services, and achieving customer delight.

• Sunder (2016a) stressed the immediate need for a useful Lean Six Sigma framework in higher education services. Similarly, Antony et al. (2012) stated possible inclusions of Lean principles and Six Sigma methodology to enhance academic and administrative processes at University.

• The team members involved in the execution of the project have to play specific roles. Team members have been identified through the “belt system” according to the level of mastery after acquiring knowledge and proper training. Team members are identified as Champion, Master Black Belt, Black Belt, Green Belt and Yellow belt. These provide efficient manpower cultivation and utilization (Park, 2003).

4.3 When and for whom Lean Six Sigma?

The US government instituted the MBNQA in 1987. Motorola awarded the first MBNQA in 1988 for successfully implementing the Six Sigma program. The program details were shared with others by Motorola, Allied Signal and General Electric (Hahn et al., 2000). As its inception, it was mostly believed that both approaches were only meant for large-scale organizations as their origin was at large-scale organizations (Brue, 2006; Byrne et al., 2007). A similar observation was reported by McAdam (2000) that continuous improvement methodologies such as Lean Six Sigma majorly implemented in large-scale organizations rather than in small-scale organizations. It is attributed to the availability of a skilled workforce, budget for training, infrastructure support, top management commitment, etc. in large-scale organizations compared to small-scale organizations (Prasanna and Vinodh, 2013).

However, as the changes took place in the field of information technology, supply chain management, other fields, etc., large-scale organizations outsourced the work to the small and medium-scale enterprises (SMEs). Also, due to stiff competition, SMEs produce better quality products at a competitive cost. As a result, SMEs are forced to use approaches such as Lean Philosophy, Six Sigma methodology and Lean Six Sigma (Antony et al., 2005). Brue (2006) claimed Six Sigma as a simple, practical problem-solving tool for business of any size and stated: “Six Sigma is not a quality fad, nor is it just for the Fortune 500.”

The articles on the implementation of Six Sigma/Lean Six Sigma approach with the focus in SMEs gradually increased in the past 10 years (Adikorley et al., 2017; Cheng and Chang, 2012; Dora and Gellynck, 2015; Gupta et al., 2018; Hung et al., 2011; Kaushik et al., 2012; Kowang et al., 2016; Kumar et al., 2013; Laureani et al., 2010; Prashar, 2015; Srinivasan et al., 2016; Yadav et al., 2019). However, it is reported that SMEs still lack behind in the implementation of such approaches in comparison with large scale organizations (McAdam et al., 2014).

4.4 Where Lean Six Sigma?

As stated earlier, Lean Philosophy developed from the studies of manufacturing practices, primarily from automobile manufacturing organizations such as TPS, whereas Six Sigma evolved and build on in different from manufacturing organization Motorola, Allied Signal and General Electric. However, both approaches evolved in manufacturing organizations; both got popular in different sectors to improve the quality of products and processes in the past 30 years. Both the approaches, as individually and combined as “Lean Six Sigma methodology,” are widely used in the manufacturing sector and the service sector. It emerged as a popular methodology in some service sectors such as health care and higher education in the recent past.

The Lean/Six Sigma/Lean Six Sigma methodology is successfully implemented in manufacturing of automotive components (Antony and Kumar, 2012; Gupta et al., 2018; Kowang et al., 2016; Kumar et al., 2006; Ruben et al., 2017; Seth and Gupta, 2005; Yadav et al., 2019), electrical part (Hung et al., 2011; Sreedharan et al., 2018; Vinodh et al., 2014), casting (Desai, 2006; Gijo et al., 2014; Kumar et al., 2013; Shanmugaraja et al., 2011), manufacturing in general (Chen et al., 2010; Kaushik et al., 2012; Li et al., 2005; Patidar and Madan, 2018; Prashar, 2015) and in construction projects (Anderson and Kovach, 2014; Johnson et al., 2006; Stewart and Spencer, 2006), printing and packaging (Chan et al., 2014; Mukhopadhyay and Ray, 2006; Rishi et al., 2018), food processing (Dora and Gellynck, 2015; Powell et al., 2017), higher education services (Thomas et al., 2017; Yu and Ueng, 2012), government R&D establishment (Kansal and Singhal, 2017), services related to healthcare (El-Banna, 2013; Taner et al., 2007), resource management services (Cheng and Chang, 2012; Shirey et al., 2018), local government services (Furterer and Elshennawy, 2005), call centre service (Laureani et al., 2010), supply chain performance (Hill et al., 2017), human resource function (Wyper and Harrison, 2002), software preparation (Mahanti and Antony, 2006) and many more. However, the authors believe that there are many more specific areas of implementation of Lean/Six Sigma/Lean Six Sigma, which are not covered above due to certain constraints.

4.5 How Lean Six Sigma?

Different tools and techniques evolved and used while implementation of Lean Philosophy, Six Sigma and Lean Six Sigma methodology in different industries. Kumar et al. studied and summarized tools, techniques and principles through exhaustive study while implementing the Lean Six Sigma methodology. These tools and techniques are value stream mapping, kanban, kaizen, 5S, standardized work, visual and workplace management, total productive maintenance, takt time analysis, single minute exchange die, production flow balancing, poka-yoke, why-why analysis, cause and effect diagram, Pareto analysis, cellular manufacturing, histogram, change management, control chart, process capability analysis, measurement system analysis, design of experiments, quality function deployment, analysis of mean and variance, regression analysis and hypothesis testing (Kumar et al., 2006).

5. Literature review

This part of the review analyses the various dimensions as a review of the literature through examine the existing literature. The approach followed in the current study is highlighted in the methodology section in detail, such as search, inclusion and exclusion criteria with figure. The study includes the articles which are published by the reputed publishing houses with the articles indexed in the SCOPUS databases. The time horizon considered for the articles is from 2000 to 2019 based on the insights from the existing reviews on Lean Six Sigma, as stated in the earlier section. Therefore, the current study covers 20 years of span compared to the earlier reviews, of which the majority of them cover the 15 years. As per adopted methodology and stage-wise scrutinization of the articles, a total of two hundred twenty-three articles has been shortlisted from 72 peer-reviewed journals for the study.

After careful examination of few review articles (Abu Bakar et al., 2015; Albliwi et al., 2015; Yadav and Desai, 2016; Yadav et al., 2017; Sunder et al., 2018), the seven key dimensions were identified for further analysis. The identified dimensions are:

• articles based on year of publication;

• articles based on the journals and publishers;

• framework;

• critical success factors;

• critical failure factors;

• industry type; and

• performance metric.

The identified seven dimensions for the current study is used to portray a picture on the research aspects such as emergence and growth, implementation approaches and important factors, key metrics used for studies, applicability in different sectors of Lean Six Sigma along with the peer-reviewed popular journals publishing the research work related to Lean Six Sigma.

5.1 Classification of articles based on year of publication

This part of the paper aims to examine the growth in terms of the number of publications in the field of Lean Six Sigma over the period from 2000 to 2019. Figure 2 shows the distribution of 223 articles based on the year of publications for twenty years selected for the study. The average number of articles published per year during the first 10 years selected for the study (2000–2009) found as 4, whereas an average 18 articles published per year were found in the area of Lean Six Sigma in past 10 years. This shows the massive growth of articles in terms of the average number of articles published per year during the past 10 years. Further from the study, it is understood that the growth of articles increased from 2006 onwards. However, the sharp and consistent growth seen from the year 2010 onwards. This examination reveals that the Lean Six Sigma methodology is increasingly becoming popular and widely adopted in different sectors from 2010 onwards.

5.2 Classification of articles based on the journals and publishers

The list of reputed journals considered for the review and the proportion of publications are shown in Table 2 with at least one article selected for the study. The articles screened from the selected databases through the keyword as Lean Six Sigma. Lean Six Sigma is applied in diverse filed of applications. Therefore the journals having Lean Six Sigma articles are found with different backgrounds, Management, Mechanical Engineering, Chemical Engineering, Medical and Social Science. Based on the research approach adopted for review, a total of 72 journals have been found with 223 articles for this study. Further, almost fifty percent of the articles, i.e. 109 articles out of 223, have been published by the following six journals: International Journal of Lean Six Sigma, Total Quality Management and Business Excellence (previously known as Total Quality Management), Production Planning and Control, International Journal of Quality and Reliability Management, The TQM Journal (previously known as The TQM Magazine) and International Journal of Six Sigma and Competitive Advantage.

Reputed publishers regularly publish articles based on Lean Six Sigma. Out of the total articles published, 41.7% of articles were published by Emerald, followed by Taylor and Francis (27.8%), Inderscience (9%), Elsevier (6.3%), Wiley (4.9%), SpringerLink (3.1%) and SAGE (2.7%).

5.3 Classification of articles based on framework

The framework is stated as a guiding torch that helps a manager provide necessary direction during the change management programs implemented in an organization (Anand and Kodali, 2010). The framework also shows interrelations between different elements, factors and constructs treated as building blocks. However, many times “model” is also used to define the steps and/or phase of implementation. The authors believe framework works as the guide in the form of providing systematic actions for the implementation of business strategy. Forty-four articles found narrating frameworks for Lean Six Sigma and integration with other manufacturing and business strategies. Further, the frameworks are classified as conceptual (C) and implemented (I). This part of the study summarizes the reviewed frameworks and their contributions in brief in Table 3. The detailed reference of reviewed articles is shown in Appendix.

5.4 Classification of articles based on critical success factors

Rockart (1979) highlighted the necessity of critical pieces of information instead of an information system to the chief executive (or decision-makers) to resolve problems. Rockart and other researchers at MIT’s Sloan School of Management developed the “critical success factors (CSFs)” approach, which was extended based on the concept of “success factors” discussed by Daniel (1961). Critical success factors defined, a few parts of activities must go right to achieve expected performance for the organization requiring critical and regular attention (Rockart, 1979). CSFs requires careful observation and crucially dealt as an ongoing activity by the management to attain the expected targets (Brotherton and Shaw, 1996). CSFs include vital issues to an organization’s current operating activities and its future success (Boynton and Zmud, 1984). CSFs are “the essential ingredients without which the initiative stands little chance of success” (Antony and Kumar, 2012). Thus, CSFs are the few important information with data helpful to the decision-makers in place of plenty of information. CSFs are termed as enablers (Dubey et al., 2016; Raval et al., 2018; Yadav and Desai, 2017a), determinants (Dora et al., 2016), drivers (Salonitis and Tsinopoulos, 2016), facilitators (Psychogios et al., 2012) and key ingredients/elements (Antony and Banuelas, 2002; Henderson and Evans, 2000). Laureani and Antony (2017) stated that leadership plays a pivotal role in Lean Six Sigma deployment and needs to be consistent at different stages with the requirement of an effective communication system. Raval et al. (2018) identified top-management commitment, involvement, and support in terms of human resource support, financial support and fund availability, helps in removing obstacles and regularly reviewing Lean Six Sigma project progress, ensures recognition and rewards for participants as dominant Lean Six Sigma enabler to transform conventional manufacturing system to Lean Six Sigma system. Similarly, Douglas et al. (2015) identified management involvement and participation as the most crucial factor in general for the successful implementation of Lean Six Sigma. Leadership and Customer focus surfaced as two significant factors in Lean Six Sigma implementation in Malaysian automotive companies (Habidin and Yusof, 2013). Through a case study based approach, Antony et al. (2018) suggested the five critical success factors for higher educational institute as strategic and visionary leadership, developing organizational readiness, organizational culture, project selection and prioritization and effective communication. A study was conducted to understand Lean Six Sigma Education for the manufacturing companies in the transition countries, i.e. Slovenia and identified the key requirements for Lean Six Sigma project managers as an innovative, an effective communicator, a positive thinker, and to have networking ability (Kavčič and Gošnik, 2016). A total of 25 critical success factors (CSFs) were studied by the authors to implement Lean Six Sigma in the 58 articles of the 223 selected articles (Table 4).

5.5 Classification of articles based on critical failure factors

In one of the early reference, Belassi and Tukel (1996) discussed an approach to find the CSFs/critical failure factors (CFFs) in project management (Belassi and Tukel, 1996). Garg and Garg (2013) defined the critical failure factors as the key aspects of Enterprise Resource Planning implementation. Further, few researchers identified the critical failure factors for the implementation of Enterprise Resource Planning in Indian and Iranian Industries (Amid et al., 2012; Garg and Garg, 2013). The CFFs are also termed as barriers (Ambekar and Hudnurkar, 2017; Desai and Patel, 2010; Dora et al., 2016; Jadhav et al., 2014; Ruben et al., 2018; Salonitis and Tsinopoulos, 2016; Shamsi and Alam, 2018; Soti et al., 2011; Tyagi et al., 2017; Yadav and Desai, 2017b), obstacles (Kwak and Anbari, 2006), inhibitors (Psychogios et al., 2012) and hurdles (Gijo and Rao, 2005). Besides, some of the recent articles identified and analyzed the critical failure factors in the implementation of Lean Six Sigma. (Albliwi et al., 2014; Ruben et al., 2018; Sreedharan et al., 2018; Yadav et al., 2018b; Yadav and Desai, 2017b). Yadav et al. (2018b) identified the 27 barriers and classified them as strategy, technology, social-cultural, organizational and individual-based barriers. Sunder (2016d) highlighted incorrect project selection as a vital failure factor in Lean Six Sigma implementation in higher educational institutes. Ruben et al. (2018) stated lack of top management commitment, lack of training and education and lack of funds for green projects as the most dominant barriers that affect Lean Six Sigma implementation with environmental considerations. Table 5 summarizes the critical failure factors identified by various researchers from time to time.

5.6 Classification of articles based industry type

As stated earlier, originally the Lean and Six Sigma evolved from the manufacturing Organizations. However, during the recent past, the service sector understood the Lean Six Sigma and realized its importance. Some of the case studies found during the present study show the applications of Lean Six Sigma in service sectors and the manufacturing sectors. The applications of Lean Six Sigma methodology are found in sectors such as construction and real estate, foundry, electronic component manufacturing, automotive, food processing, power, textile, chemical processing, pharmaceutical and manufacturing in general. The implementation of Lean Six Sigma improved product quality by reducing defects and variations, enhancing productivity by reducing cycle time and waste elimination, and reducing the consumption of materials. The implementation of Lean Six Sigma in service sectors increased significantly, particularly in healthcare service and higher education services. Other service sectors include the banking and finance sector, government service, software industry, airline services, call center, outsourcing, human resources and facility management. The improvement in different services reported by the various authors are reducing the patient waiting time in the outpatient department (Gijo and Antony, 2014), decreasing the cesarean section rate (Ren et al., 2016), reducing the risk of healthcare infection (Carboneau et al., 2010; Improta et al., 2018), reducing the patient stay in hospital (Improta et al., 2018; Toledo et al., 2013), services related to higher education institute (Sunder, 2016d), reducing cycle time in business process outsource organization (Ray and John, 2011), customer satisfaction in banking service (Sunder and Antony, 2015), etc. Different types of industries in which the Lean Six Sigma methodology applied as a case study are summarized in Table 6.

5.7 Classification of articles based on performance metric

The performance metric is the measurement of the performance of an organization in a particular area. A well-defined performance metric is an essential requirement for projects and showcases the achievement of improvements in the specified area. Based on the focus of the study, the performance metrics be classified as customer-oriented and financial metrics (Schroeder et al., 2008). Kumar (2008) identified three fundamentals metrics, i.e. yield, defects per million opportunities, and sigma level for the measures of process capability, number of defects in a process and quality of the output produced respectively for the six sigma projects. Some of the performance metrics found in case studies are as process cycle efficiency in engineering support services (Ratnayake and Chaudry, 2017), reduce rejection in account opening application in bank (Sunder, 2016c), cost of poor quality (Sreedharan and Sunder, 2018), reducing patient waiting time (Al-Zain et al., 2019; Bhat et al., 2014; Gijo and Antony, 2014), increase the first-call resolution ratio (Laureani et al., 2010) and many more. Therefore, the understating of performance metrics is an essential part of the adoption of Lean Six Sigma methodology. Table 7 summarizes various performance metrics considered in the case studies reviewed during this study.

6. Concluding remarks

This review article has examined the literature in the field of Lean, Six Sigma and Lean Six Sigma to understand the historical developments and analyzed the research work. The significant finding on Lean Six Sigma determined from the current review study is noted in this section. Also, the research gaps have been described at the end of this section.

6.1 Significant findings

1. Lean Six Sigma has emerged as one of the prominent quality improvement methodologies in the last fifteen years. The simultaneous use of Lean and Six Sigma has a synergized effect in terms of eliminating waste and reducing the variations.

2. Lean Six Sigma as a business strategy and with the prime focus on the customer is extensively adopted by different sectors worldwide in the early part of the 21st century. The current analysis revealed that the number of articles in the field of Lean Six Sigma had increased significantly by 80% in the last decade, which shows research avenues available in this field. The publications of articles on the Lean Six Sigma boost in developing countries such as India, Malaysia and Brazil in the past few years.

3. Climate change is one of the biggest environmental concerns in the present era with other environmental concerns, which has to foster the focus on sustainable development or sustainability. It is found that researchers had proposed frameworks integrating the Lean Six Sigma methodology with concepts such as green/environment, life cycle assessment, sustainability, innovation, integrated system of management and energy management to achieve the synchronized benefits.

4. The study revealed that researchers had proposed the conceptual frameworks for implementation of Lean Six Sigma, whereas few of them also validated through a case study approach. It is found that 66% of frameworks are conceptual; in contrast, 34% frameworks are empirical and implemented through the case study as the most preferred approach.

5. The critical success factors had a decisive role in attaining the organizational goals in the successful implementation of Lean Six Sigma. The commitment, involvement and support of top management, education and training, Organizational culture, linking LSS with business strategy, and customer and employee involvement emerged as the vital CSFs in the implementation of LSS. Similarly, lack of knowledge about the LSS, lack of resources, lack of top management commitment, resistance to change and lack of effective training appears to be the CFFs for the LSS implementation.

6. Though the origin of Lean and Six Sigma took place in manufacturing organizations, the present study found applications of Lean Six Sigma as a continuous improvement strategy even in services sectors. Further, improvements in services reported with the implementation of Lean Six Sigma are reduction in infection rate in surgery, waiting time in OPD and hospital stay post-surgery in the healthcare sector, teaching effectiveness, curriculum development and library services in the education sector, first call ratio in a call center, processing in food products, etc.

7. Besides, some of the other findings are as follows:

   • It is reported that the journal titled International Journal of Lean Six Sigma by the Emerald publishing house is one of the leading journals as the maximum number of articles, i.e. 33 articles found from it this review.

   • During the current study, it is found that Jiju Antony has made significant contributions in the field as the maximum number of articles published in refereed journals, reviewed.

   • Around sixty percent of the articles reviewed are of case study type from all reviewed articles. Further, 74.3% case study based articles published are from 2011 to 2019 compared to 25.7% from 2000 to 2010, which confirms the popularity and adaptability of Lean Six Sigma as a methodology for improvement in different sectors, including the service sectors.

   • It is observed that the majority of the research articles published are authored by academicians and researchers (80% articles) compared to very few authored by professionals and consultants (20% articles).

6.2 Research gaps and direction for future work

• No article reports with a generalized framework approach for Lean Six Sigma in some specific sectors such as the ceramic industry, diamond polishing industry, foundry, higher education and government. The efforts are to be made to have a segment-specific generalized framework.

• The top management involvement and support, education and training, culture aspects and organizational resources have a pivotal role in the successful implementation of Lean Six Sigma. However, the impact of such factors for sector-specific industries in diverse economy such as developing countries be further investigated.

• The integration of Lean Six Sigma in the era of digitization with approaches such as artificial intelligence, data science, machine learning, big data, cyber-physical system and cloud computing can be explored as no articles found in the present study.

• Minimal involvement of consultants is observed in the development of new aspects of Lean Six Sigma. Therefore, the research in different aspects of Lean Six Sigma with the direct involvement of consultants need to be focused in future study.

• There is scope to study comparing the CSFs and CFFs in a similar type of organization in different parts of the world. The impact of technological developments on factors for implementation of Lean Six Sigma should be explored in developing countries such as India.

6.3 Limitations of the study

The current research study comprises with few of the limitations. The articles were searched with keywords as “Lean,” “Six Sigma” and “Lean Six Sigma” in article title and from the Elsevier, Emerald, Taylor and Francis, Springer, Inderscience, Wiley and SAGE publishing house. Though the articles with a focus on Lean Six Sigma existed/published, relevant articles could have been missed due to the limitation of search methodology and limitation of accessibility of the articles to the authors.

In conclusion, this study aimed to investigate the adoption of Lean Six Sigma in different sectors worldwide and evaluate the success achieved in implementation. Impressive growth in terms of articles related to Lean Six Sigma has been found in the past decade. It has emerged that Lean Six Sigma is a methodology for overall improvement in the organizations, including the service organizations. The authors believe that this article will help develop an initial understanding of Lean, Six Sigma and Lean Six Sigma and provide the research insights on Lean Six Sigma to the beginners such as students, researchers and entry-level professionals.

Figures

Figure 1.

Methodology for the study

Figure 2.

Classification of articles based on the year of publications

Table 1.

Existing reviews on lean six sigma

Sr. No.	Name of author/s	Description of study
1	Albliwi et al. (2014)	The authors reviewed 56 articles from 1995–2013 and investigated the critical failure factors for Lean Six Sigma in different sectors and reported main failure factors from different perspectives
2	Abu Bakar et al. (2015)	The authors investigated Lean Six Sigma deployment's critical success factors from 13 papers between 2010–2015 and identified the five significant critical success factors through analysis
3	Albliwi et al. (2015)	This article includes a review on Lean Six Sigma for the manufacturing sector, included 37 articles from the top journals covering from 2000–2013 and discussed the motivation factors, impending factors, benefits, and limitations of the implementation of Lean Six Sigma in the manufacturing sector from 19 case studies
4	Yadav and Desai (2016)	A categorized review on Lean Six Sigma was carried out using 189 articles from the period of 2001–2014. The authors highlighted the growth of Lean Six Sigma from perspective such as country, journal and publishers, growth, research method, industrial sectors, enablers for implementation and active authors
5	Lande et al. (2016)	The authors examined the critical success factors for Lean Six Sigma in the context of small and medium enterprises from articles ranging from 2000–2015. It identified the most critical twelve factors
6	Sreedharan and Raju (2016)	The authors reviewed 235 articles ranging from 2003–2015, with a focus on Lean Six Sigma in different industries based on five dimensions
7	Raval and Kant (2017)	This article summarized the Lean Six Sigma frameworks from viewpoints such as novelty, source, verification and its approach and vital constructs from 58 frameworks
8	Yadav et al. (2017)	The authors critically reviewed 26 Lean Six Sigma frameworks from the timeline of 2000–2017, revealed the inconsistencies in the frameworks and proposed construct for the Lean Six Sigma framework
9	Muraliraj et al. (2018)	The authors presented an annotated review of Lean Six Sigma, including 261 articles from 2000–2016, and highlighted the vital essential aspects
10	Sunder et al. (2018)	The authors conducted a review using 175 articles on Lean Six Sigma with a focus on Services industries and reported six dimensions

Table 2.

List of selected journals considered for review

Name of Journal	No. of publication
International Journal of Lean Six Sigma	33
Total Quality Management & Business Excellence (10) + Total Quality Management (10)	20
Production Planning & Control	19
International Journal of Quality & Reliability Management	16
The TQM Journal (10) + The TQM Magazine (1)	11
International Journal of Six Sigma and Competitive Advantage	10
Quality Engineering	9
International Journal of Productivity and Performance Management	7
International Journal of Production Research	6
Journal of Evaluation in Clinical Practice	6
International Journal of Production Economics	4
Benchmarking: An International Journal	4
International Journal of Productivity and Quality Management	4
Quality and Reliability Engineering International	4
Journal of Manufacturing Technology Management	3
Leadership in Health Services	3
International Journal of Business Excellence	3
Business Process Management Journal	2
International Journal of Health Care Quality Assurance	2
Journal of Advances in Management Research	2
Journal of Industrial Engineering International	2
Journal for healthcare quality	2
Arabian Journal for Science and Engineering	2
Other Peer-reviewed Journals with at least one article published are International Journal of Project Management, Journal of Chemical Health & Safety, Journal of Cleaner Production, Journal of Operations Management, Procedia - Social and Behavioral Sciences, Procedia CIRP, Procedia Engineering, Procedia Manufacturing, Radiotherapy and Oncology, Technovation, Assembly Automation, Industrial Management & Data Systems, International Journal of Operations & Production Management, International Journal of Quality and Service Sciences, Journal of Business Strategy, Journal of Engineering, Design and Technology, Journal of Modeling in Management, Kybernetes, Management Research News, Measuring Business Excellence, International Journal of Lean Enterprise Research, International Journal of Quality and Innovation, International Journal of Services and Operations Management, American Journal of Medical Quality, Concurrent Engineering: Research and Applications, International Journal of Engineering Business Management, Journal of Industrial Textiles, Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, Progress in Transplantation, Global Journal of Flexible Systems Management, The International Journal of Advanced Manufacturing Technology, Quality & Quantity, Assessment & Evaluation in Higher Education, Construction Management and Economics, International Journal of Construction Management, International Journal of Management Science and Engineering Management, Journal of Applied Statistics, Journal of the Operational Research Society, Journal of the Textile Institute, Production & Manufacturing Research, Journal of Clinical Laboratory Analysis, AIP Conference Proceedings, Applied Mechanics and Materials, Chemical Engineering Research and Design, International Journal of Mechanical and Production, Journal of Advanced Manufacturing Systems, Journal of Facility Management and Research, Journal of Management in Engineering, Quality Management Journal	1
	223

Table 3.

List of frameworks with a summary

Author (Year)	C/I	Contribution	Article reference no.
Ben Ruben et al. (2018)	C	This paper proposed a five-step LSS framework with a focus on the environment. The study includes the aspects related to performance measurement, decision-making, linking LSS with other manufacturing strategy and application	170
Mustapha et al. (2019)	C	This article highlights the key elements for the implementation of LSS in developing countries involving the qualitative approach and based on multiple case studies through interviews	143
Raval et al. (2018)	C	In this paper, an integrated (ISM and Fuzzy MIMIC) framework proposed based on 40 enablers of LSS identified from the literature and through expert opinion	163
Raja Sreedharan et al. (2018)	C	This article proposed Green Lean Six Sigma Model involving structured literature review and focus group study (Black Belt and SCM group). The proposed model defines three stages, i.e. procurement, production, and distribution, sub-divided into 17 steps	186
Raja Sreedharan et al. (2018)	I	This paper explored four LSS Awareness constructs in the Indian context through surveys and validated through empirical study	185
Raja Shreedharan and Sunder (2018)	I	Authors conceptualized a novel framework named 'SDMMAICS framework,' i.e. selection, define, measure, map, analyze, improve, control and sustain for the manufacturing sector along with the activities and tools for each phase followed with two case studies	187
Moya et al. (2018)	I	An assessment method developed to access the capabilities of SMEs for implementing the LSS project is explained in the paper. The same was validated through two case studies in France and Chile	141
Sunder and Antony (2018)	C	This paper presented with a conceptual framework with a focus on structured problem solving and practice-based experiential learning at the universities. The basis of the proposed framework is on the project management approach comprising of six steps	195
Yadav et al. (2018)	I	A hybrid framework for LSS, i.e. a fuzzy AHP – PROMETHEE based on 27 barriers and 22 solution approaches framework developed in the paper. The developed framework was tested for suitability through case application	218
Zwetsloot et al. (2018)	I	An integration of LSS with data science presented as a framework for an extensive financial services firm in The Netherlands in the paper. With an integration of two road maps, i.e. data science and LSS, the paper showcase the differences among traditional LSS and data science LSS and applicability through case studies	223
Aldairi et al. (2017)	C	Through the research article, the authors proposed a conceptual framework on knowledge-based system with Lean Six Sigma for sustainable building maintenance (KB Lean6-SBM) using hybrid integration with analytical hierarchal process and gauge absence prerequisites	5
He et al. (2017)	I	A model proposed showing the relationship between Six Sigma practices and organizational innovation performance. The empirical study highlighted that Six Sigma be adopted to enhance the organizational capabilities in organizational innovation	92
Cherrafi et al. (2017)	I	Five stages, 16 steps framework (GL2S), integrating green and Lean Six Sigma was developed to enhance sustainability performance, i.e. economic, environmental and social performance. The outcome of the implementation of the said framework showed encouraging results	48
Mahato et al. (2017)	I	This paper highlighted an integration of the simplex method of optimization with traditional DMAIC as a proposed hybrid framework as DMAIoC framework. The authors showed improvement in filed quality rejection in the mass production of consumer goods through optimizing the parameters at minimum investment	135
Mkhaimer et al. (2017)	I	The authors showcased the applicability of a proposed Lean Six Sigma energy management model through a single case study in a pharmaceutical company in Jordan. The model provided guidelines for effective system implementation along with sets of analytical and statistical tools	139
Antony et al. (2016)	C	An investigative study was carried out to learn the relationship between LSS and innovation based on an interview in UK based ten companies. It was reported that LSS significantly influences innovation at the process/product/service level with the enhancement of innovative capabilities	25
Arcidiacono et al. (2016)	C	As a part of a structured roadmap, a four-phase model, i.e. assessment, monitoring, sustainability, expansion (AMSE), proposed to govern the deployment of LSS to ensure the sustainability of the LSS program for different sectors	27
Arunkumar and Dillibabu (2016)	C	The authors developed a Kano Lean Six Sigma model with an object to enhance the software quality at no extra effort, cost and time	28
Garza-Reyes et al. (2016)	I	This article proposed an LSS framework for ship loading activities at the iron ore industry. The reduction in ship loading time is achieved through the implementation of the LSS framework	73
Bhamu and Sangwan (2016)	C	A three-phase framework for lean manufacturing covering the entire supply chain proposed in the paper. The framework consists of pre-implementation, implementation and post-implementation phases for implementation	36
Sunder (2016)	C	The author suggested Inform - Involve - Influence (3I) model for stakeholder management for Lean Six Sigma project management during implementation in service organization, especially in banking and financial services	192
Tsironis and Psychogios (2016)	C	This article presented a multi-factor model for Lean Six Sigma application in service organization based on the synthesis of critical success factors	209
A. Boon Sin et al. (2015)	C	A theoretical model developed to establish the relationship in knowledge creation processes in the Six Sigma project and its impact on organizational performance by using structural equation modeling	39
Alves and Alves (2015)	C	This article proposed a model integrating principles of lean manufacturing and sustainability. The model comprised of five-stage – 20 steps as an integrated system of management (ISMA)	9
Timans et al. (2014)	C	The authors revised a proposed model using a multi-method triangulation approach for the implementation of LSS in SME. As a part of the revision, a five-phase approach was reduced with three phases with thirteen steps	205
Banawi and Bilec (2014)	I	This paper developed a framework integrating three approaches, Lean, Green, and Six Sigma, to improve quality with an environmental focus. As a framework, a three-point part of DMIAC steps linked with value stream mapping of lean and life cycle assessment of green validated through a case study in the construction sector	31
Assarlind et al. (2013)	C	This paper proposed a model as 'company production system house.' It stressed on improvement teams, expert forums, workgroups, process forum and division management team	29
Prasann and Vinodh (2013)	C	A lean anchored design, measure, analyze, improve and control, sustain model (LADMAICS) proposed and discussed a hypothetical case study with emphasized scientific management of LSS	155
Chakraborty and Leyer (2013)	C	The authors proposed a company framework for financial services	43
Karim and Arif-Uz-Zaman (2013)	I	This article developed an effective methodology with a leanness evaluation metric and validated through a case study	109
Psychogios et al. (2012)	C	The authors proposed a multi-factor conceptual approach for Lean Six Sigma implementation in the telecommunication service context through a case study approach	158
Psychogios and Tsironis (2012)	C	A framework as L6σ proposed showing the interrelationship between critical factors affecting the application of LSS in the airline industry	159
Gnanaraj et al. (2012)	I	This article proposed a model having five levels for the implementation of LSS in SMEs. The proposed model named Deficiency Overcoming Lean Anchorage Define Measure Analyse Improves Control Stabilise (DOLADMAICS)	81
A Pal Pandi et al. (2012)	C	A model proposed for a higher educational institute with ten critical factors for the implementations	149
Karthi et al. (2011)	C	The authors proposed an integrated model, “L6QMS 2008 model,” with integration of Lean, Six Sigma and ISO 9001:2008 standard suggesting 20 steps for implementation at a minimum expenditure and efforts.	110
Kumar et al. (2011)	C	A five phases – twelve steps framework for Six Sigma implementation for SMEs developed with a triangulation approach with the help of three case studies	120
Pepper and Spedding (2010)	C	This paper proposed a conceptual model integrating the Lean and the Six Sigma methodologies	151
Soti et al. (2010)	C	This article identified eleven enablers as a building block of Six Sigma through interpretive structural modeling (ISM)	182
Anand and Kodali (2010)	C	This paper proposed an exhaustive conceptual framework for lean manufacturing with sixty elements	12
Jones et al. (2010)	C	In this paper, a framework developed concerning contextual elements as leadership and the methodological techniques as plan, do, check, act	108
Jeyaraman and Teo (2010)	C	A framework with the following four phases: LSS formation, LSS execution, LSS promotion and LSS sustention, for implementation, was proposed in this paper. Different activities are grouped into ten factors for LSS implementation success	105
Chakravorty (2009)	I	This article proposed a six steps implementation model of Six Sigma based on strategic and tactical decisions	44
Deshmukh and Lakhe (2009)	C	Training – to define, measure, analyze, improve and control (T-DMAIC) model proposed with critically highlighting the model enriched with training for the SMEs	64
Kumar et al. (2006)	I	This article proposed a framework with five steps integrating three methodologies such as Lean, Six Sigma and total productive maintenance (TPM)	119

Table 4.

Critical success factors for Lean Six Sigma

Critical success factors	Article reference no.	Frequency
Top management commitment, involvement and support	143; 163; 115; 34; 188; 170; 13; 222; 68; 172; 122, 66; 124; 67; 104; 206; 126; 60; 149; 41; 105; 118; 17; 117; 134; 123; 21; 16; 93; 271; 150; 209; 158; 96; 56	35
Education and training	143; 34; 188; 170; 222; 68; 66; 137; 124; 104; 159; 149; 105; 118; 117; 134; 123; 68; 93; 217; 158; 96; 56; 209; 114; 40	26
Organizational culture	143; 163; 188; 13; 222; 68; 122; 66; 124; 67; 126; 159; 41; 118; 134; 123; 21; 16; 217; 150; 209; 158	22
Linking LSS with business strategy and customer	188; 170; 13; 68; 124; 67; 86; 206; 126; 60; 159; 149; 41; 118; 17; 134; 21; 16; 217; 150; 209	18
Employee involvement and participation	34; 188; 170; 13; 166; 68; 137; 124; 159; 149; 118; 117; 16; 150; 209; 40	16
Frequent communication	143; 188; 68; 66; 104; 206; 41; 105; 118; 217; 150; 40; 96; 56	14
Recognition, Incentives and Rewards	143; 163; 170; 13; 166; 105; 134; 16; 93; 217; 209; 40; 158	13
Leadership	128; 124; 86; 69; 126; 159; 118; 2; 127; 128; 209; 96	12
Project management skills	128; 13; 222; 68; 67; 206; 41; 123; 16; 114; 96	11
Project prioritization and selection	170; 68; 122; 137; 124; 41; 105; 134; 2; 16; 158	11
Understanding tools and techniques	188; 13; 68; 124; 67; 60; 159; 41; 16; 217	10
Organizational infrastructure	188; 170; 68; 67; 60; 41; 17; 134; 16; 93;	10
Financial funds for operation expenditure	163; 128; 34; 170; 68; 104; 105; 2; 217	9
Supply chain focus	115; 188; 13; 68; 86; 206; 41; 16; 217	9
Selection of top talented people	163; 170; 13; 66; 69; 105; 114; 56	8
Long-term strategy	115; 34; 115; 68; 124; 217	6
Focus in metric	34; 86	2
Company's vision	115; 206;	2
Information and knowledge sharing	170; 143	2
Linking Six Sigma to a benchmarking program	166; 105	2
Established LSS dashboard	104; 105	2
Need for a more dynamic model	115;	1
Daily routine management	166	1
Quality information and analysis	86	1
Structured improvement procedure	86	1

Table 5.

Critical failure factors for Lean Six Sigma

Critical failure factors	Article reference no.	Frequency
Lack of top management commitment	181; 143; 170; 10; 210; 172; 102; 182; 117; 134; 19; 171; 216	13
Lack of knowledge	143; 184; 170; 210; 103; 222; 172; 159; 182; 118; 79; 19	12
Lack of resources (poor infrastructure)	170; 10; 210; 103; 206; 62; 118; 17; 117; 134; 79; 216	12
Lack of training and development Lack of effective training	181; 143; 184; 170; 10; 118; 17; 117; 119; 171; 216	11
Resistance to change	143; 170; 10; 222; 102; 206; 118; 17; 134; 119; 171	11
Wrong projects selection	181; 174; 10; 62; 17; 79; 191	7
Lack of clear vision and plan	184; 182; 123; 79; 216; 158	6
Lack of Leadership	170; 210; 102; 206; 62	5
Improper communication (communication of data)	170; 10; 181; 171; 216	5
Large scale investment in training	10; 172; 102; 159	4
Insufficient financial resources	10; 222; 171; 216	4
Lack of synergy between LSS and Business strategy	181; 171; 216	3
Lack of cross-functional team	184; 79; 216	3
Lack of employee involvement	170; 118; 158	3
Employee resistance	159; 62; 216	3
Lack of suitable data	62; 134; 79	3
Premature discontinuation of LSS	181; 102	2
Unmanaged expectations	181; 62	2
Lack of link between LSS and customer needs	181; 134	2
Large Tool Set	181; 19	2
Sustaining benefits of improvement	181; 19	2
Narrow view about LSS	10; 222	2
Lack of tangible results	62; 17	2
Time consuming	174	1
Staff turnover in the middle of the project	174	1
Part-time involvement in Lean Six Sigma projects	174	1
Poor selection of candidate for Training	216	1
Poor Success rate of project	181	1
Misuse of statistics	181	1
Lack of performance measurement system	216	1
Wrong selection of LSS Tool Set	216	1
Satisfaction with current quality	181	1
Employee's fear of job cutting	181	1
Industry-specific issue	159	1

Table 6.

Articles based on industry type

Industry type	No. of publication
Manufacturing	36
Foundry	8
Automotive	5
Textile	3
Food processing	5
Chemical processing	3
Construction	9
Electronic Mfg.	6
Wood furniture	1
Power sector	2
Pharmaceutical	2
Healthcare services	22
Higher education	12
Banking/finance	3
Government/public utility	6
Services in different areas	20
BPO service	2
Software company	2

Table 7.

Performance matrices

Performance metric	Article reference number
Reduce the defects in different manufacturing processing such as tire, injection molding, gloves, casting, gear, switch, riveting, bush, flat panel display, grinding, machining, textile processing and wood furniture, yarn packaging, pharmaceutical	84; 83; 63; 3; 169; 199; 11; 160; 77; 161; 74; 212; 121; 30; 20; 214; 59; 179; 113; 80; 211; 176; 168; 203; 58; 54; 130; 119; 200; 88; 142; 213; 7; 78; 26; 135; 111; 220; 91; 154
Increase yield in glass manufacturing, dairy products, grinding	219; 153; 20
Reduce the cycle time in production planning, grinding, BPO, chemical processing, telecom manufacturing and Services, engineering support service	15; 45; 20; 47; 164; 178; 46; 1; 200; 138; 173; 175; 55; 85; 162; 101; 190
Reduce the waste in iron ore and construction projects, reduce cost of poor quality	199; 100; 31; 187
Reduce time at activities such as healthcare facility, gas distribution, inpatient days in surgery, ship lading, delivery time, in aerospace manufacturing, patient management activities such as registration, wait time and discharge time, mold change, construction, procurement, processing in government services, reduce biohazardous waste, policing service, book search time at library, production cost	177; 82; 140; 73; 204; 11; 37; 76; 70; 131; 189; 57; 72; 53; 4; 22; 24; 191; 52; 167; 145; 38
Enhancement of services in activities such as library services, meter reading, services in Higher Education such as onboarding process, IT and Finance service, Teaching-learning process, air-purifying respirator process, teaching effectiveness, first call ratio in a call center, production process, healthcare services, deep drawing and sheet metal process, software development, housing design, human resource services, reduce customer complaint, baggage handling at the airport	197; 157; 198; 51; 221; 129; 90; 133; 215; 180; 147; 144; 132; 87; 8; 19; 148; 116; 152; 125; 31
Increase productivity per operator and a first-time pass rate, increase dispatches of medical reports, increase overall equipment effectiveness	178; 130; 173; 33; 50
Reduce order to receipt time in an aerospace maintenance repair and overhaul facility	94
Medication administrative errors	18; 208; 99
Achieve an optimum rate of acidity in yogurt production	89
Reduce hospital stay in hip replacement surgery, in the emergency department, in liver transplant	97; 71; 207; 146
Reduce field failure of tractor assembly	156
Reduce overfill and rework in gingerbread processing	65
Improve customer satisfaction score for banking call center, payment processing accuracy in banking	194; 196; 193
Reduce infection rate in the surgery department, breast daily repositioning case in radiotherapy	140; 136; 98; 49; 42
Reduce de-mineralized water consumption in Thermal power plant	112; 180

Appendix. Articles reviewed for the current study

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