Lean Six Sigma competency frameworks: evaluating the competencies required for the Lean Six Sigma Black Belt

After the Second World War, the conference of national standardizing organizations that established ISO was held in London from 14 to 26 October 1946. It was also in this year that the American Society for Quality Control (ASQC, changed to ASQ in 1997) was formed. The need for standardizing standards was obvious during the time of rebuilding the international community. Quality standards are defined as “documents that provide requirements, specifications, guidelines, or characteristics that can be used consistently to ensure that materials, products, processes and services are fit for their purpose” (ASQ, 2022). ISO defines a standard as “the distilled wisdom of people with expertise in their subject matter and who know the needs of the organizations they represent” (ISO, 2021). More broadly, work on ISO-based quality systems and their integration with Lean and Lean Six Sigma shows that standardization can improve comparability and discipline, while also creating implementation and fit challenges across contexts (ISO 9000:2015; International Organization for Standardization, 2015; Stevenson and Barnes, 2001; Chiarini, 2011a; Karthi et al., 2011; Bacoup et al., 2018; Sá et al., 2020).

ISO 18404 has triggered debate among scholars, practitioners and standard developers about the feasibility and desirability of standardizing Lean Six Sigma competence and auditing it in practice (Antony et al., 2021, 2023; Oudrhiri et al., 2022; Sony et al., 2025). Prior work assessed the potential benefits and limitations of ISO 18404 and highlighted that the standard can be experienced as prescriptive and challenging to apply across diverse contexts (Antony et al., 2021, 2023). A subsequent response from contributors close to the development of ISO 18404 argued that earlier critiques relied on a selective interpretation of the standard and its intent (Oudrhiri et al., 2022). Overall, peer-reviewed empirical applications of ISO 18404 remain relatively limited compared with the widespread use of certification bodies of knowledge, and recent evidence suggests that applicability and uptake vary across settings (Sony et al., 2025).

Given the inconsistencies in existing Lean Six Sigma competency frameworks and the evolving demands of organizations and practitioners, this study seeks to explore the following research question:

1. How can Lean Six Sigma competency frameworks be standardized and positioned to align with international qualification standards to support the evolving demands of organizations and practitioners?

The article is structured as follows. The next section explores the existing literature on the subject, establishing the foundation for the research objective. This is followed by Methodology and the Results. The proposed Metamodel is followed by the Conclusion.

Despite its long history, there is no consensus on the standard for Lean Six Sigma and its certification (Antony et al., 2017; Hollingshed, 2021; Laureani and Antony, 2012). Although Lean and Six Sigma are historically independent business improvement methodologies, the synergies of combining them have led to the integrated methodology “Lean Six Sigma” starting from the beginning of this century (George, 2002). That integration has also been discussed conceptually, in service settings, and in deployment models that stress the need to align tools, organizational infrastructure and leadership (George and George, 2003; Salah et al., 2010; Hilton and Sohal, 2012). While Lean focuses on waste reduction in processes from customer's perspectives, Six Sigma focusses on the variance reduction and how this effects the process outcomes felt by the customer, thus combined to Lean Six Sigma as both methodologies are complementary in their nature (Antony et al., 2022; Arnheiter and Maleyeff, 2005; Arumugam et al., 2012). Nowadays, the predominant opinion is that Lean and Six Sigma are integrated into Lean Six Sigma (Antony et al., 2017; Snee, 2010) and are applied and studied as one (Lameijer et al., 2021).

The deployment of Lean Six Sigma is done by the Black Belts, who are trained in the stepwise breakthrough strategy. This is supported by an organizational infrastructure differentiating between the people accountable and responsible for the changes, like sponsors, champions and process owners (Chiarini, 2011b), and the people improving processes at several levels requiring different knowledge and skills. Earlier work on Black Belt deployment and competency-based implementation similarly emphasizes the importance of role clarity, deployment capability and broad technical depth (Ingle and Roe, 2001; Huq, 2006; Pyzdek and Keller, 2018). In literature, commonly accepted roles for these Quality Management Professionals are the White Belt, Yellow Belt, Green Belt, Black Belt and Master Black Belt (Laureani and Antony, 2012). There are several bodies for certification and the most well-known are the American Society for Quality (ASQ), International Association for Six Sigma Certification (IASSC), the Council for Six Sigma Certification (CSSC) and the International Lean Six Sigma Institute, abbreviated as ILSSI (Salentijn, 2021). The Lean Competency System (LCS), which originated from the Lean Enterprise Research Centre (LERC) at Cardiff University, has its focus on Lean (Elias, 2016). Besides these independent certification bodies, there are also a lot of institutes or companies offering their own certification for their own programs. Table 1 provides a high-level comparison of major competency frameworks and standards included in this study.

ISO 18404 has triggered debate among scholars, practitioners and standard developers about the feasibility and desirability of standardizing Lean Six Sigma competence and auditing it in practice (Antony et al., 2021, 2023; Oudrhiri et al., 2022; Sony et al., 2025).

Nonaka and Takeuchi (1995) assert that knowledge manifests in two fundamental forms: explicit and tacit. Explicit knowledge consists of organized material, including frameworks, procedures and standards, which can be recorded in certification programs and ISO recommendations (Davenport and Prusak, 1998). Contrary to explicit knowledge, tacit knowledge is developed by experience, intuition and problem-solving skills that are difficult to capture in words (McInerney, 2002). Determining the competences for professionals in process improvement applying Lean Six Sigma, the challenge is how to integrate these two forms of knowledge. Explicit knowledge can be written down, and tacit knowledge requires activation and experience (Baskerville and Dulipovici, 2006). The absence of a consistent standard for LSS certification results in discrepancies in the competencies of qualified Black Belts (Antony et al., 2017; Laureani and Antony, 2012).

By structuring LSS knowledge in a formal framework, we create a shared baseline. This improves comparability across certification programs. Knowledge taxonomies also facilitate knowledge transfer across institutions and organizations (Young and Chapman, 2010). Competency-based learning requires a clear framework that specifies what professionals should be able to do at each certification level (Lameijer et al., 2021). Moving from knowledge and skills to competence helps ensure people are prepared for their role in practice (Thomas et al., 2017). Adjacent work in quality management and competency management likewise suggests that formal competence frameworks can make expectations, development paths and role transitions more explicit (Martin et al., 2021; Vakola et al., 2007). Structuring competences allows organizations and professionals flexibility and the ability to adapt to changing circumstances and create a shared language and comprehension (Davenport and Prusak, 1998), enabling the successful implementation of continuous improvement (Snee, 2010). In an Industry 4.0 context, Lean Six Sigma training needs to go beyond knowledge alone. Professionals need to know how to use and apply new technologies or methods like Lean Six Sigma as part of the daily routine (Antony et al., 2022, 2024; Citybabu and Yamini, 2023). The European Qualifications Framework (EQF) and the Dublin Descriptors are two well-known reference points that we utilize to make it easier to compare the different levels of certification. Both discuss the competencies and skills students should acquire in educational institutions, vocational training, and professional certification (Bologna Working Group on Qualifications Frameworks, 2005; CEDEFOP, 2021; European Commission, 2022). We use EQF because it provides an established, transparent language for positioning professional certification requirements to internationally recognized competence levels, while still allowing contextual tailoring (Lester, 2015).

This study adopted a three-stage mixed-methods design. In the first stage, the literature to date was reviewed and analyzed. In the second stage, a Delphi study was conducted to refine the findings into a meta-model synthesizing existing models and expert insights. To explore the application of the meta-framework, a pilot study was conducted in the third stage during the 2024–2025 Dutch ILSSI Black Belt exams, following competency-based education. These exams replaced traditional multiple-choice tests with competence-based assessments. Students' written evaluations (n = 200) were thematically analyzed. The literature review was based on the preferred reporting items for systematic reviews and meta-analyses statement, PRISMA (Moher et al., 2009), and the different phases were followed (Figure 1). To structure and analyze the LSS Competency Frameworks available to date, a systematic literature review (SLR) was performed in July 2022 and updated in January 2025.

The string used to search for academic articles was: (“Lean Six Sigma” OR “LSS” OR “Six Sigma”) AND (“Black Belt” OR “competenc*” OR “competenc* framework” OR “body of knowledge” OR “certification” OR “ISO 18404”). The inclusion and exclusion criteria are mentioned in Table 2.

The comparative review focused on three dimensions: areas of agreement (e.g. technical/statistical capabilities and knowledge of process improvement), areas of divergence (e.g. leadership, change management and digital/Industry 4.0 competencies), and the degree to which frameworks combine tacit and explicit knowledge elements.

Using a benchmarking lens, we coded the frameworks and compared them across categories to see how well they consistently allow organized comparison of practitioner competencies. That benchmarking perspective is consistent with both classic and more recent benchmarking literature, which treats comparison not merely as ranking, but as a structured way to identify recurring practices, gaps and areas for adaptation (Camp, 1989; Castro and Frazzon, 2017). To refine these classifications into a validated meta-framework, a Delphi study with 15 experts was conducted. Details of this process, including the rounds, mapping to the EQF and Dublin Descriptors, and final consensus, are presented in the section Delphi Study. Based on the Delphi study with experts, a meta-model was developed and piloted during the academic year 2024–2025. During the pilot, evaluations were collected at the end of the examination. Handwritten responses were entered into Word by an administrative assistant and then analyzed through coding by a researcher. This yielded 200 useful results. A coding scheme was used to organize the analysis of the competency frameworks, classifying them into four groups: technical/statistical skills, methodological knowledge, leadership and change management skills and new skills emerging from Industry 4.0. The validity of the study was strengthened by combining a strategic literature review, a Delphi study, and piloting the resulting meta-model in professional practice.

Given that the Black Belt plays a central role in an organization's improvement strategy (Antony and Karaminas, 2016; Hoerl, 2001; Harry, 1998; Ingle and Roe, 2001), this research focuses on how different competency frameworks define the necessary skills and knowledge for this role. Multiple academic studies, standards and other relevant works have been analyzed to determine what the standards are for a skilled Black Belt. All the articles and documents regarding the subject under research have been analyzed and categorized and the results can be found in Appendix A. The outcomes of this literature review form the basis for the expert validation in Stage 2 (Delphi).

This provides a clear overview for understanding both the similarities and differences between the several standards. Most of them emphasize technical capabilities, like applying statistics and the DMAIC for problem solving (e.g. ASQ, CSSC, IASSC), while others focus more on change management and leadership (e.g. Antony et al., 2018; Hallam et al., 2018; Laureani and Antony, 2021; Vakola et al., 2007). Additionally, some models suggest a more holistic and evolving role for Black Belts in modern business environments due to developments like Industry 4.0 (Chiarini, 2020; Citybabu and Yamini, 2023; Antony et al., 2024).

Using Sanghi's (2007) approach to competency mapping, we identified the core competencies that recur across Lean Six Sigma frameworks. In short, the overlap is strong, but the emphasis differs per framework, which is in line with broader work on competency management in both quality and organizational change domains (Huq, 2006; Martin et al., 2021).

1. Technical skills: statistical analysis and process control (covered by all frameworks; see also Pyzdek and Keller, 2018).

2. DMAIC and Lean tools: included in all frameworks, but with varying depth (Antony, 2020; Uluskan, 2016).

3. Problem-solving and decision-making: root cause analysis and process improvement appear in all frameworks; decision-making is more explicitly emphasized in ASQ.

4. Leadership and change management: project leadership and team management are present across frameworks, but interpreted differently; the same holds for change management and broader organizational change (Laureani and Antony, 2021; Vakola et al., 2007).

The Delphi method was chosen as it enables a structured way for experts to build consensus. This is especially useful for complex topics where the evidence base is fragmented and key terms are used inconsistently. A three-round design was used to iteratively refine competency statements and their positioning, until stability in the panel's ratings and comments was reached (Hsu and Sandford, 2007; Okoli and Pawlowski, 2004).

Building on the European Qualifications Framework (EQF) and the Dublin Descriptors, the Delphi panel positioned Lean Six Sigma Black Belt competencies at EQF Levels 6–7, aligning them with the corresponding Dublin Descriptors. Appendix B and Appendix C, respectively, include the levels for the EQF and the Dublin Descriptors. Fifteen Lean Six Sigma Black Belts (LSSBBs) underwent a three-round Delphi assessment to guarantee the validity and robustness of the competency mapping. Selected members of the expert panel were chosen based on their certification status and Lean Six Sigma implementation and training experience, guaranteeing that the insights acquired were both academically grounded and practical. The profiles of the LSSBBs are included in Appendix D.

The Delphi study was conducted in three rounds. In Round 1, experts assessed whether the proposed Dublin Descriptors and related competency profiles aligned with Lean Six Sigma Green Belt (LSSGB) and Black Belt (LSSBB) requirements. In Round 2, the panel mapped the competencies to the European Qualifications Framework (EQF), providing an internationally comparable classification. In Round 3, the model was refined by the experts. This process resulted in consensus on twelve core competencies, mapped to the appropriate EQF levels. While there was strong consensus on problem diagnosis, statistical tools, DMAIC and process change management, divergent views arose on innovation, communication, cooperation and ethics. The expert-driven approach guarantees that the proposed competency model reflects both academic rigor and practical applicability, bridging the gap between theoretical learning and industry needs. On the numerous important skills that LSS practitioners should have, the Delphi panel agreed strongly:

1. Problem Identification and Diagnosis. The capacity to separate symptoms from root causes and apply methodical problem-solving techniques.

2. Competency in applying statistical tools and process control techniques will help one drive decisions.

3. Using DMAIC, Lean tools and Design of Experiments (DoE), among other methodologies, solution design and implementation help to maximize processes.

4. Process change management is the application of improvements in an organizational context that guarantees scalable and sustainable nature of process changes.

5. Research and analytical skills include the capacity to investigate extensively, examine facts and create insightful analysis.

6. Supporting teams by means of cooperative efforts and directing process improvement projects helps to engage stakeholders and play advisory roles.

Although most competencies were agreed upon, on innovation, cooperation, communication and ethics the opinions differed (Figure 2).

The Delphi results imply that, depending on the complexity of the position, LSSGB competencies match EQF Level 5 and LSSBB competencies match Levels 6 and 7 (Figure 3). EQF Level 5 (LSSGB) operational and tactical competencies driven by implementing systematic approaches in specified surroundings. EQF Level 6 (LSSBB: Standard Role) Competencies stressing independent analysis, decision-making and leadership within process improvement teams. Strategic competencies encompassing organization-wide Lean Six Sigma deployment and enterprise-level process transformation comprise EQF Level 7 (LSSBB: Advanced Role/Master Black Belt).

Competencies provide a high-level overview of what someone can do or is capable of, and consist of the dimensions knowledge, skills, responsibility and autonomy. Collectively, these dimensions present an organized way of viewing the ways in which competencies show up in order to organize education programs (Table 3).

To test the model in real life, a pilot study was conducted to test the competence-based framework. For this goal, the multiple-choice exams for the Black Belt on behalf of ILSSI in the Netherlands were replaced by competence-based assessments. This move toward more application-oriented assessment is consistent with broader work on competence-based and practice-oriented assessment design in professional education (Brinkman-Staneva, 2015; Rodriguez-Paz and Sayeg-Sánchez, 2023).

Relevance and Authenticity: A majority of students, approximately two-thirds of all responses, emphasized the authenticity of the competence-based exam. The exam is generally perceived as more realistic, challenging and relevant than traditional multiple-choice tests. For example P1 wrote: “The exam forces me to apply Lean Six Sigma concretely in practical situations, which I find more challenging but also more instructive than memorizing answers.” Real-life scenarios make the cases more realistic. As P2 stated: “The cases resemble situations in my daily work, which makes me feel competently assessed. It requires not only knowledge, but also insight and understanding of application.” Still, some students struggled with this concrete application to practical situations. For example, P3 stated: “At times I missed more direct questions about definitions, but I see the value of the broader, application-oriented approach that demands more than factual recall”.

Application and Critical Thinking: More than half of the students highlighted that the competence-based exam required them to reason and apply concepts rather than simply memorize facts. As P4 remarked: “The exam forces me to apply Lean Six Sigma concretely in practical situations, which I find more challenging but also more instructive than memorizing answers.” P5 added: “It is no longer about reproducing knowledge but about showing that you can apply it.” Still, some valued the choices forced on MC more: “For some questions I would have preferred more structure, multiple choice feels more comfortable for this (P6).” The competence-based nature stimulates critical thinking and the application of Lean Six Sigma concepts rather than merely testing factual knowledge.

Comparison with Multiple Choice: Almost half of the students compared the competence-based exam with traditional multiple-choice tests. Many emphasized that the absence of guessing was a strength, as it demanded genuine understanding, though some also noted it made the exam more difficult when they were uncertain. As P7 wrote: “The absence of the option to guess, forces genuine knowledge, but it also makes it harder when in doubt.”

Perceived Challenges: Around two out of five students reported difficulties with the competence-based format. They pointed to the open-ended nature of the questions, time pressure, and the absence of clear grading rubrics as particular challenges. As a student stated: “I find weighing different scenarios useful, although at times I felt uncertain about what the ‘intended’ solution was (P8).” Despite challenges, most students endorsed the new exam as a more valid representation of Lean Six Sigma practice: “Tougher, but this is what prepares you for the real world (P9).”

This study responds to persistent variation in Lean Six Sigma Black Belt competency expectations across certification bodies and the continuing debate about whether competence can be standardized and audited. By synthesizing 27 frameworks, validating core competencies through a Delphi panel, and piloting a competence-based assessment, the study offers a structured meta-model that complements both certification bodies' bodies of knowledge and the international standard ISO 18404.

Comparison with ISO 18404 shows overlap in core technical and change-related competencies (e.g. problem diagnosis, data acquisition and analysis, project management and stakeholder management). However, several widely used frameworks and academic studies emphasize additional areas that are less explicit in ISO 18404, including belt-structure design (e.g. Yellow Belt), structured experimentation (DoE/DFSS) and broader leadership and facilitative capabilities required to mobilize and sustain change. These differences support viewing ISO 18404 as a useful reference point rather than a complete representation of contemporary Black Belt competence. Positioning competencies against EQF levels and the Dublin Descriptors strengthens comparability by linking certification expectations to established learning-outcome descriptors. This helps clarify the distinction between a “standard” Black Belt role (often aligned with EQF Level 6) and more advanced, enterprise-level deployment responsibilities (often aligned with EQF Level 7).

The results also indicate a growing expectation that Black Belts can operate in data-rich and digitally enabled environments. While traditional frameworks focus on statistical tools and DMAIC, current practice increasingly requires data literacy, governance awareness and the ability to work with digital diagnostics and AI-supported analysis (often discussed under Quality 4.0) (Citybabu and Yamini, 2023; Antony et al., 2024). We therefore include digital and data-enabled improvement competencies as an explicit cluster in the proposed framework.

The framework can be used in several ways. For certification bodies and training providers, it helps to compare curricula and assessments using the same “language”, and to make competence levels explicit, for example, through EQF positioning. For organizations and HR, it gives a clear structure for role profiles, hiring criteria and development paths for improvement professionals, which is consistent with adjacent competency-framework work in quality management and organizational change (Martin et al., 2021; Vakola et al., 2007). For candidates, it works as a simple mirror: where are the gaps in technical, methodological, leadership and digital skills, and what learning would actually close them? And for exam and assessment designers, it supports tasks and rubrics that test application and judgment in realistic situations, instead of testing memory.

This study has a few clear limitations. First, both the Delphi panel and the pilot were mainly conducted in a Dutch context. That context can shape how people look at role expectations and what they consider a “good” assessment format. Second, the evidence base is a mix of peer-reviewed research and practitioner and certification documents. That is also how competence is described and codified in practice, but it can mean that the dominant voices of providers are reflected more strongly than others. Third, digital competencies are still an emerging domain and the target is moving fast, so parts of this area may change quickly. Future research could validate the framework across countries and sectors, test predictive validity by linking competency profiles to project and organizational outcomes, and study how competence-based assessment reliability can be improved through clearer rubrics and assessor training. Further work is also needed to refine and update the digital/Quality 4.0 cluster as standards such as ISO 9001 evolve.

This study set out to deal with a very concrete issue: despite the centrality of the Black Belt role, there is no broadly shared competency framework that is both explicit and usable across providers. We therefore brought together 27 existing models, translated them into a single meta-model, tested its content through a Delphi study with certified experts, and then piloted the framework in a practice setting. Across models and experts, the technical core is remarkably stable. Competencies around DMAIC, statistical thinking, and structured problem solving attracted strong agreement. The picture becomes less uniform once leadership and change management enter the framework. Experts recognize these competencies as essential, but differ in how they should be specified and assessed in a way that is fair and comparable. The same holds for emerging digital and Industry 4.0-related skills: they are increasingly expected, yet still developing in terms of shared definitions and level descriptions.

A key contribution of this work is that the framework is not only a list of competencies, but also a levelled interpretation. By positioning Black Belt competencies explicitly against the European Qualifications Framework (EQF) and the Dublin Descriptors, the framework supports clearer benchmarking across training programs and certification bodies. The pilot adds an important practical signal: competence-based assessment was experienced as more authentic and more relevant than multiple-choice testing, but also more demanding. It shifts the emphasis from recognizing “the right answer” to demonstrating application and judgment.

The supplementary material for this article can be found online