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Lean Six Sigma

Vishwadeep Khatri
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Lean is an ever evolving philosophy based on proven principles and practices aimed at the elimination of waste (improving efficiency) with the objective of making every step, task, & activity create value for the customers. Lean is a continuing process of change involving everyone in the organization. Lean principles originated at Toyota.


Six Sigma


Six Sigma is a data driven problem solving approach with the objective of increasing profits by reducing the defects (improving effectiveness) in a process. Defect reduction happens in two ways - first, reducing the variation in the process, second, by moving the actual mean closer to the target mean. 
Six Sigma is all of the following
Metric: 3.4 defects per million opportunities
Methodology: DMAIC / DMADV frameworks
Management System: all business units are aligned to key improvement efforts
Philosophy: encompasses all of the above and a state where it becomes a way of life.


Lean Six Sigma


Lean Six Sigma is a combination of tools, techniques and best practices from both Lean and Six Sigma philosophies with an objective to simultaneously improve both Efficiency and Effectiveness of a process.



An application oriented question on the topic along with responses can be seen below. The best answer was provided by R Rajesh on 30th September 2018. 


Applause for all the respondents- Manjula Pujar, Sitaram, Tina Arora, Saranya Subramanian, Yogesh Rathod, Manoj Kumar Alagesan, Rajesh Chakraborty, Kalpesh, 


Q. 97  Lean and Six Sigma are two different approaches for process excellence, where Lean focuses on efficiency and Six Sigma focuses on effectiveness. In the more recent times, Lean and Six Sigma have been combined to form Lean Six Sigma. What are some of the advantages and disadvantages of combining the two approaches? Highlight with relevant examples.


Note for website visitors - Two questions are asked every week on this platform. One on Tuesday and the other on Friday.

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Let us discuss here, how Six Sigma and lean operates (in a brief manner) and how Lean and Six Sigma are used in conjunction with each other and what are the advantages and disadvantages in using them together.


Lean focuses on waste elimination,continuous improvement and Six Sigma focuses on reducing or minimal variation and thereby focuses on improvement. Both approaches are used for improvement of processes.


Let us dwelve further on these.


Six Sigma is a process-oriented problem solving methodology (and even defined as a management technique) which focuses on getting minimal variation(or optimised result) of the process( which produces the product/ service) such that it results in 3.4 defects per million opportunities. The six sigma approach includes of defining the problem, measuring the current process in place, analysing the problem, improve (on the existing process/design(Create new if process cannot be improved), optimize(if needed), then establish the control on the process. This is how a six sigma project is executed. At every stage/phase of a six sigma project, there are a set of quality tools(and in some stages, statistical control tools come into play as well), that may be required to be used. There is an important equation in six sigma which is Y=f(x) where 'Y' is the Dependent Variable and 'x' is the independent variable. 'x' is a factor(input) that can shape 'Y' (outcome). Assume that there are quite a few web pages in your web application which takes 15 seconds to get loaded (assuming there is no solution found for 6 months- customer though not happy understands the practical issues and is ok to have this six sigma approach). For the customer, the response time (Y) of the web pages should be less than or equal to 3 seconds. Imagine if this is the need of the customer. There could be factors such as Database efficiency, 3rd party components, interfaces with legacy systems, etc... one of which (or few of them) when improved can fasten the response and therefore the response time can match with the customer needs. These factors are the Vital 'X' factors. Therefore, Six Sigma focuses on attacking the vital factors that will produce the necessary outcome.    


Lean is about waste elimination and continuous improvement of process(es). A process (which produces the product or service) that requires improvement is analysed threadbare - in terms of value added steps, non value added steps and value enabled steps. The non-value added steps of that process are eliminated. 7 Wastes is one such technique in lean which talks about waste elimination. There are many such lean techniques like 5S, Kaizen, Kanban... Kaizen apprach is used for continuous improvement activities.


Let us compare and contrast some of the key aspects/characteristics Six Sigma and Lean approaches.


1. Six Sigma approach is very expensive when compared with Lean approach    
2. Six sigma focuses primarily on minimal or reducing variation and thereby improvement on a process/product/service whereas Lean focuses on waste elimination,continuous improvement
3. Six Sigma is time-consuming as it will have to gather data, analyse (lot of statistics involved) and can involve lot of dedicated people when in comparison with lean approach.
4. Six Sigma has multiple stages(phases) of approvals (pre-defined toll-gate reviews) when compared with techniques of Lean approach
5. Realising the Outcome(or Return on Investment) of the Six Sigma will take long time(after quite a few months or a year or so even) when compared with using a lean   approach
6. Acquiring Six Sigma knowledge might have a relatively deeper learning curve when compared with lean approaches- primarily due to the amount of tools used in each  phase of Six Sigma and also the concepts surrounding various aspects of Six Sigma.
7. Six Sigma is not right approach for immediate results, whereas lean techniques can be used for immediate/quick visible results (in general).


Let us see the advantages of combining Six Sigma and Lean approaches together:

1. By combining both the approaches which is called the Lean Six Sigma approach, the focus shifts to both waste elimination and also variation reduction.
2. During analyse phase of Six Sigma project, Value Stream Map technique helps in analysing the needed steps only for a process (which is under study). It  identifies unnecessary steps. This, in addition to attacking the vital 'X's.  This will be quite useful in cases where cycle time/processing time/execution time needs to be reduced.
3. Six Sigma tools are interspersed with lean techniques/tools across the phases of Lean Six Sigma. Therefore the six sigma team can afford to use the right or best  tool/technique according to the needs.


We will see the advantages of a Lean Six Sigma approach with an example.


Problem Statement: The time taken to deliver the software code (by an IT organisation) to an external Quality Assurance(QA) team was more across several projects (which are running in a traditional waterfall model) and the end-delivery of these projects to the customer took considerable time due to code quality issues as QA team found more bugs and thereby the development team took time to fix the bugs . . This was happening for the past 6 months. The customer was unhappy with the situation. The mgmt decided to have a six sigma project to tackle this issue , in agreement with the customer. The objective was to fix the code with highest code quality (<2% bugs-only minor ones)  and provide 100% of time-bound deliveries in 5  months of time.


A Six Sigma team was formed to address this issue and they decided to attack this with a lean six sigma approach.


Let us get into the crux of the issue.

Elaborating onto the software development processes, developer1 wrote her code in her machine(local) and tested that code(called unit testing which was done via automation using JUnit framework).

Developer1 now waited for her project lead to review. Meanwhile developer2 wrote his code in his machine(local) and did the unit testing. He also waited for the lead to review. Similarly other developers had written their parts of the code. Often , the lead was busy in other project related activities. Now these codes were awaiting the lead's review before they could be put into the Code repository from which the developed codes was built by a Continuous Integration server and put into an integrated environment, where once again the lead reviewed the integrated codes and all the codes were automatically unit tested as well (when the codes were built by the Server. Note: Build is nothing but compilation of the software code - if it is successfully done, then it would normally programmed to deploy the code in an environment where users of the software application can test it. If the build is not successful, then the errors will be notified to the relevant teams. During the build process,  automation things are integrated as part of that so that they are automatically triggered.Here Unit testing automation triggered). Since the integrated code contains all the codes from all developers, for which the review happens, there was no need for a separate review to be done (by the lead) for each of the codes developed by the respective developers . Therefore that waiting done by each developer for the lead to review his/her code was not necessary and that was eliminated as a Non-Value Added step using the Value-Stream Map analysis.  This helped in increasing the speed(reduced the time) to deliver the code to the external Quality Assurance  (QA)team.

Next now was to fix code quality issues and thereby increasing the quality of the code and adhering to the timelines to be delivered to the customer.  There were no. of bugs (errors) in the code (given by the teams) to the QA team. To address this , the Six Sigma team came up few approaches after lot of analysis and evaluating multiple options and going through lot of criteria. They chose Test-Driven Development (TDD - it talks about writing test cases first and then do the coding- in a nutshell) and automation of functional testing using Selenium framework. While TDD was needed for codes that were written newly (to avoid issues in future), usage of Selenium (with the help of internal testers) resulted in developers finding functional defects(bugs) and fixed the issues before it reached to the external QA. This resulted in time savings as the external QA team found minimal or negligible bugs and therefore the time taken to deliver the code to the customer , for each of the projects were on-time and the customer was pleased with the results. The key to the success was the elimination of waste step involved in this entire process and then subsequently the improvement made on the automation for functional testing and redefining the coding way by introducing the TDD approach. Thus we can see how lean Six Sigma can be harnessed


Let us see the disadvantages of combining Six Sigma and lean approaches together.

1. There are quite a number of tools that need to be analysed and learned while trying to find best fit when using lean six sigma approach. Multiple tools need to be known
2. Lean techniques are gaining popularity now in non-manufacturing/automobile industries but still not every industry is fully harnessing it yet. Learning curve will be there for people who has been involved in traditional six sigma approach  


Consider the example that was discussed above on improving the delivery and quality of the IT projects. The Six Sigma project was delivered on using a Lean Six Sigma approach. But the project lead(BB) and also the team was not too much aware of the nuances of many of the lean techniques as lean technique was not still getting popularised in their IT organisation. Often they struggled to find the right techniques at the initial stages of the project. This gave less confidence to the stakeholders/project sponsors who were hoping to see a good positive result from this Six Sigma project.  The project however turned out well after that initial stuttering.  Nevertheless the bottom line was that there was some kind of learning curve for that team.



We have seen both how lean and Six Sigma works at a high level. Also we have seen how Lean Six Sigma can help in streamlining a process. While using a Lean Six Sigma approach, there are pros and cons, the positives in this approach outweigh the negatives in using that approach.

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Advatages of combining lean and six sigma

As said Lean  focuses on efficiency which  is removing  'unwanted ',which helps to improve the productivity . Six sigma takes it forward to sustain the efficiency. 

Combination of both gives more opportunities to work on like Services levels, Attrition' Customers satisfaction 

Conversation of Sales. 



There are no major disadvantages in combination of both 

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The Six Sigma is a top to bottom driven approach, where usually the improvement Ideas are based on the problem statement or the desired project objective as usually taken by the leadership, while lean is a bottom to top approach where the Ideas of improvement comes from the employees and people close to the work ,


The traditional perception has that MBB, BB,GB and the Process Improvement teams are totally depended on Stats and methodologies that are not fully understood by the employees, while the lean followers are more likely to find improvement ideas with simple tools and techniques and changes that help processes in a far easier fashion and solve, So there was this constant cross hairs as to which was the best method, marrying both with lean six sigma has helped in the following:


  • Making employees at all levels connect with process improvement culture and teams, with small lean events and workshops and making them better engaged with the processes improvement teams , would be a investment when bigger projects like a BB,GB projects needs their engagement
  • Generate more idea with using some of the methodologies of Six sigma with lean, Ex: The DMAIC frame work has been successfully coupled with lean, for  idea generation and Improvements
  • The change management has been easy with lean taking the idea of Improvement into the employees , and while encouraging these lean practices it has been helpful in identifying greater Six Sigma BB,GB projects 

The above being the case, the management needs to be aware that encouraging one system over the other, Lean over Six Sigma , to be able to showcase more gains and Ideas, than few GB BB projects will be a mistake best avoidable


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In my view, Top 3 advantages and disadvantages of merging two approaches are as below :




1. A combined approach ensures that both efficiency and effectiveness metrics are tracked and delivered as a package by the process excellence manager. 

2. For senior management that is not too comfortable with statistics, lean brings in simple to comprehend tools and applications that are material to explain and easy to implement. 

3. All projects, big or small, long term or short term can be brought under the purview of implementation by merging both the approaches. 




1. Process Excellence team may try to oversimplify or overcomplicate the project by not balancing both approaches. 

2. It could lead to creation of two groups within the team - ones that advocate Lean, others Six Sigma risking the project progress on critical path. 

3. Team members of Process Excellence team may need to get certified on both approaches which may not be seen as a welcome cost by the management. 




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Inorder to answer the question of this week. Let us first remind ourselves what lean and six sigma mean. 

Lean, as the name suggests, means to streamline processes so that there is minimal waste and cost in operations (efficiency). Six sigma on the other hand, aims at fulfilling all customer needs, delighting and sustaining a customer base in a highly competitive environment (effectiveness).


Remember, the more efficient army effects it's own victory. This holds good for every business out in the market. Today with globalisation, market determines the price of a product and hence, the producer/service provider is left with lesser opportunity to gain profit margin through direct pricing. However, with the same technology which has enabled globalised market, there is more scope now than ever to reduce cost and thereby increase profit while still being competitive in the market. Hence the confluence of Lean with Six Sigma becomes essential and advantageous for competing organisations.


While on the flip side, the only disadvantage of implementing Lean along with Six Sigma is that, it takes time and effort to initially align, mobilise and start governing people and such a streamlined process to attain effective implementation and control to excel in customer satisfaction and gain a good sustained profit margin.

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When we are looking forward to attaining process excellence there are many ways, in which we can excel in our process, the most commonly used are lean and six sigma


Lean focuses on improving efficiency (Performing or functioning in the best possible manner with the least waste of time and effort).

Lean focuses on identifying and eliminating 3M's,

  • Muda; any activity or process that does not add value (e.g, the 8Wastes)
  • Mura; unevenness in the process and supply chain (e.g, when companies ramp up production to meet targets, even when there is no customer demand)
  • Muri; overburden (e.g, unnecessary stress to our employees and our processes)

The strategy of lean is to eliminate the wastes(Muda) caused by Mura(Unevenness) and Muri(Overburden) by using tools like 5S, Kaizen, 8Wastes, Poka-Yoke, Kanban(Pull system), SOP, Visual Standard

Simply Lean is doing things right (Inherent process capability_Cp)


Six Sigma(Accuracy);

Six Sigma focuses on improving effectiveness (Producing the intended or expected result)

Six Sigma is a vehicle for strategic change (Both Transformational & Transactional), it provides businesses with tools to improve the capability of their process and ensures the process is aligned with customer requirements by reducing variation in the process 

Simply SixSigma is doing the right things (Resultant process capbility_Cpk)


Lean Six Sigma; 

Lean Six Sigma is an integrated concept of Lean and Six Sigma, it focuses on reducing the variation by eliminating wastes.




Nothing is superior to one another both concepts have their own traits, the need of these concepts may vary depends upon the situation 


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In today's Business world , with the Start up culture in boom, most of the entrepreneurs are open to new concepts and techniques that will help them to achieve business excellence and drive it closer to their vision.  For Business Excellence Experts and people who have studied both the approaches/ Philosophies i.e Six Sigma and Lean , understand that Six Sigma complements Lean philosophy by providing data centric tools and know-how to eliminate wastes and catalyze continuous improvement in the existing business processes . Both approaches, essentially have the same goals of making the existing systems more efficient.  If combined justly as per the need of the business, Six Sigma methodology can be used to reduce the variation in the process and then combined the Lean philosophy application to  focus on the improvement in the value stream  and the customer experience  by highlighting  on key value adding areas.


Advantages of combining the 2 approaches is that:

- Each the approaches mitigate or subdue the cause of resistance for the other approach; The "fear of statistics" that is associated with six sigma is countered by the simple day to day improvement methods that Lean proposes and on the other hand the the fear that Lean puts forth about lay offs due to cutting on non value add activities and using automation is mitigated by six sigma approach which provides statistical inputs through reliable tools on how the effectiveness can be improved.


- Incorporation of 2 overriding philosophies which seeks to maximize the value-added content of all operations, supported by  training and education with defined hierarchies and dynamc leaders. It helps to create a single " language" across all the levels in teh organisation, wherein the data and analysis is a top down process and teh ideas and implementations works on a bottom up process


- Continuous  evaluation of systems to ensure a global optimization and not limited to local optimization combined with variation reduction within the process.


- Effective and Efficient Management decision-making that bases decision on relative impact on the customer supported  by data-driven methodologies.


Disadvantages or constraints :


-  Any organisation adopting LSS will need to be engaged in too many time- and resources consuming projects, that don't necessarily provide IMMEDIATE sufficient results, as the new generation of CEOs prefer . This can lead to a early abortion the approach. This undesirable situation arises mostly due to the complexity of Six Sigma concepts which iis heavily based on statistics and BIG DATA , which many organisations lack as the existing processes are not on desired maturity level. Infact, most of teh times this issue is pointed out to be responsible for the incompatibility of the two approaches .

- If not overseen by a qualified Business excellence expert , an LSS programme could easily fall under the domination of immediate costs saving, rather than focusing on customer experience. Indeed, though it is understood in both theories, in practice, the necessity of rapid cash results is predominant,  due to a lack of a policy deployment.




It is obvious that LSS would work theoretically, helping companies to tackle root causes of quality concerns and customer dissatisfaction, as well as high costs and inefficiency. However, this strategy is mostly based on the combination of two other approaches, which were not existing earlier in the organisation. As organizations are already struggling to succeed in implementing Lean or Six Sigma as the theory explains it, LSS seems all the more a biggest challenge. It is therefore imminent that there is defined method and a need of clarification on a "how-to" guide for LSS implementation, integrating both approaches and not just adding them together. This needs to be done by an expert with cooperation from teh management


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Ø  Advantages of combining six sigma with lean:

Sigma is output or goal oriented (Effective) & Lean is trimming the process(Making it efficient).

Six Sigma (Effectiveness) always comes first or precedes Lean (Efficiency). Every process first has to be effective then efficient.

Ex:  Combination LSS

In a Manufacturing industry if Certain Unit produces 100 units against target of 100 Units Per Day With X cost then it is Effective.


a.       If the same Unit produces 100 unit per Day with X-1 Cost

b.       If Same unit produces 150 Units per day With X

c.       If Same unit Produces 150 units per day with X-1 cost

Hence, Lean accelerates Six Sigma to Achieve Goal. Lean adds a Dimension to Six Sigma

Ø  Disadvantage of combining six sigma with lean:

The Only disadvantage could be One Order of application, one cannot first apply lean and then Six Sigma.

In such case he again need to realign the Lean to optimize new process.

& one cannot parallel work on both, First system need to be established then optimizes.

Lean comes in Implementation (Strategy Implementation) of Six Sigma (Strategy Formulation) Approach of DMAIC.


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