Six Sigma is a great production methodology based on good discipline and use of a set of tools and techniques. The Six Sigma concepts help to gain great process improvement and aim at defect prevention in the process in which it is used.

At basic level, Six Sigma helps one to measure defects, identify their root causes and then use its tools and techniques to prevent such defects. Thus Six Sigma aims to improve a process so that the root causes of defects are removed and the process becomes more predictable and produces less defects. To achieve this, Six Sigma uses a set of tools, techniques and methods. All Six Sigma projects follow a well-defined series of steps to give quantified results as one expects.

Six Sigma is a well defined, structured and disciplined business methodology. Six Sigma is known to greatly improve 1. customer satisfaction, 2. production efficiency and 3. organizational profitability.  It does so by 1. streamlining operations, 2. eliminating defects, 3. improving quality and 4. stabilising processes.

What is 3.4 DPMO?

The term ‘Six Sigma’ owes its origin to statistical measurement of quality. Simply put, a process is called Six Sigma if 99.999666% of all opportunities to produce exactly same result are totally defect-free. In other words, there can only be 3.4 defects per every million opportunities. Hence it is shortly known as 3.4 DPMO.

SIX SIGMA Milestones in Time:

1986: Around this time, SIX SIGMA was first developed by Motorola Inc.

1991: SIX SIGMA registered as U.S. Service Mark 74,026,418

1995: SIX SIGMA was adopted as an integral part of work at the General Electric.

Late 1990’s: Two thirds of Fortune 500 organizations in the world adapted Six Sigma to some degree.

2005: Motorola said they saw over US$17 billion in savings due to Six Sigma.

2011: ISO published the first standard “ISO 13053:2011” defining Six Sigma.

A High Level Overview of SIX SIGMA:

Six Sigma identifies two methods for its projects: DMAIC and DMADV. Both are based on Deming’s Plan-Do-Check-Act Cycle.


In Six Sigma terms, the phrase DMAIC stands for Define Measure Analyse Improve Control.

DMAIC helps to improve, optimize and stabilise a process in just 5 steps in a specific order. As the name suggests, these 5 steps are 1. Define 2. Measure 3. Analyse 4. Improve and 5. Control. It is important to note that DMAIC is driven by statistical data. It means all aspects of the method are measured and quantified to ensure success. The 5 steps can be understood broadly as below.

Define: During this phase, the basics of the project are clearly defined to give clarity to the project team and others. Terms like customer requirements, project goal, project scope, project resources etc. are clearly defined here. It is vital to understand Voice of the Customer (VOC) and Critical To Quality (CTQ) in this phase for all projects.

In the first step of ‘Define’ phase of DMAIC, 1. the Business Opportunity is validated to make sure it makes sense to progress and 2. the CTQ (Critical To Quality) is identified to know what makes good quality.  This is achieved by capturing the Voice of the Customer (VOC), translating VOC into Y’s and then selecting the key Y’s. An agreed upon Project Charter for each key Y is a good example of output from this phase.

The second step of ‘Define’ phase of DMAIC, involves: 1. Project Storyboarding and 2. Team Charting. This is achieved by creating: 1. Business Case, 2. Project and Goal statement, 3. Project Scope, 4. Project Milestones and 5. Resource Plan.

The third step involves SIPOC and As-Is Process Mapping. At a high level, all such process can be explained as 4 steps, 1. Business Problem => 2. Statistical Problem => 3. Statistical Solution => 4. Business Solution.

Voice of the Customer (VOC) is a statement made by the customer about a product or service to be delivered to them.  The common Voice of the Customer (VOC) methods are: 1. Surveys, 2. Interviews, 3. Focus Group, 4. Suggestions and 5. Observations.

Once the customer requirements are known, they are put to KANO analysis to know which rank higher. Here, Requirements are sorted as: 1. Basic, 2. Performance, 3. Delighter, 4. Indifferent, and 5. Reverse.

As per Six Sigma, the term SIPOC stands for Suppliers, Inputs, Processes, Outputs and Customer. A SIPOC diagram enables one to identify: 1. the process inputs (X’s) and 2. outputs(Y’s), 3. process owner, 4. customer and 5. supplier. SIPOC also names the process boundaries.

A Six Sigma Process  map is a graphical representation of what bits and pieces make the process. In Six Sigma terms, Process maps make it very easy to understand the relationship between  inputs and outputs of the process. There are three common types of process maps in use: 1. Process Flow Chart, 2. Deployment Flowchart and 3. Alternate Path flowchart.

Measure: In the ‘Measure’ phase, first a baseline is established using factors that can be measured as numbers. The same factors are measured again at the end of the project to know what kind of change is caused by the project. If the measured change is as desired, the project is a success, else a failure.

In other words, the team frames a way to quantify the factor that needs to be improved and defines a method to measure the same again at the end of the project.  The difference that the project makes to the business can be expressed quantitatively too. All relevant data is collected and saved.

Thus the Measure phase of Six Sigma DMAIC has the below steps: 1. (a)Identify Project’s possible Y’s and (b) Data Collection Strategy, 2. Validate a Measurement System and 3. Determine the Process Capability.

There are two types of measures that play a role in DMAIC: 1. Effective Measures and 2. Efficiency Measures.

There are two types of data involved: 1. Qualitative data and 2. Quantitative data. Qualitative data can be 1. Nominal, 2. Ordinal or 3. Binary and Quantitative data can be 1. Discrete or 2. Continuous.

Sampling is a vital part of Measure phase as it is easier to do and found to be accurate. Sampling methods can be broadly classified into two: 1. Probability sampling and 2. Non-probability sampling. Probability Sampling can be 1. Simple Random Sampling, 2. Stratified Random Sampling, 3. Systematic Sampling or 4. Cluster Sampling and Non-probability sampling can be 1. Convenience Sampling, 2. Judgement Sampling, 3. Quota Sampling or 4. Snowball Sampling.

Analyse: This phase involves a detailed analysis of the current process and the data from above to find and study the areas that need to be worked upon to achieve the project target. Things like a root-cause if the project is aiming to address a problem or some elements if the project is aiming to achieve an improvement there etc. can be good examples. This step finishes when the team identifies points that need to be addressed in order to achieve the main target of the project.

The main step of this phase is to Identify Project X’s and then statistically validate the same.

Improve: In this phase is appropriate actions are planned and taken on the points that have been identified in the previous steps. The team takes action and implements the changes  as suitable either in a small area of the whole system or the whole system. Thus the team finds a solution, takes all actions needed to take the process from current state to the desired future state and proves that the solution works as planned.

There are three steps to this process: 1. Generate potential solution and assess their failure mode, 2. Validate pilot solutions and 3. Process control and Risk analysis.


In this phase, the Six Sigma team sets up a control system to monitor the process in its new state so that it is sustained. In cases where the team notices any deviation from the normal, they put an action plan in place to correct the process before it results in more defects.

There are two steps to this phase: 1. ‘Execute control plan and Finalize documentation’ and 2. ‘Communicate to business results and sign-off to close the project’.


In Six Sigma terms, DMADV stands for Define Measure Analyse Design Verify.

DMADV is a methodology that when applied to a new system, makes it Six Sigma level. There are 5 sequential steps that DMADV mandates for a new system to achieve an end-result that has six sigma tools and techniques built-in. As the name suggests, these 5 steps are 1. Define, 2. Measure, 3. Analyse, 4. Design and 5. Verify.

Define:  In this step, the project goal, requirements, resources timelines etc. are defined clearly so that the Six Sigma project team is fully aware of the same.

Measure: This step consists of activities to identify and quantify the relevant data i.e. factors of the system that need to be acted upon and influenced to achieve the project goal.

Analyse: In this step, analysis is performed to find out how the outputs change with the inputs. Thus, the team understands the way to progress with the approach to improve the process.

Design: Based on the observations made so far, a Six Sigma solution is designed that gives the desired result.

Verify: Here, the new solution is verified to make sure it gives the desired result.  This can be in the form of small pilot projects  initially and full Six Sigma project eventually.


In Six Sigma projects, we find two types of leadership roles as named below: 1. Initiative Leadership and 2. Project Leadership. Initiative Leadership leads the Six Sigma initiative in a project or organisation. Project Leadership makes sure that the project uses the Six Sigma tools and techniques for its progress.


Six Sigma uses numerous tools to achieve the goals of defect reduction and process improvement. Some of these tools are:

  1. 5 Whys
  2. ANOVA Gauge R&R
  3. Axiomatic design
  4. Business Process Mapping
  5. Chi-squared test
  6. COPIS Analysis
  7. Correlation
  8. Cost-benefit analysis
  9. CTQ tree
  10. Design of experiments
  11. Fishbone or Ishikawa diagram)
  12. General linear model
  13. Pareto chart
  14. Regression analysis
  15. Root cause analysis
  16. Scatter diagram
  17. SIPOC analysis
  18. Swim lane Map
  19. Taguchi methods
  20. Value stream mapping

SIX SIGMA Certifications

The below are the common Six sigma Certifications: 1. Six Sigma Yellow Belt, 2. Six Sigma Green Belt, 3. Six Sigma Black Belt, and 4. Six Sigma Master Black Belt.

Six Sigma Yellow Belt

A Six Sigma Yellow Belt is a professional who is 1. in a part-time Six Sigma role on small improvement projects or 2. supporting improvement projects as part of a team.

Six Sigma Green Belt

A Six Sigma Green Belt is a professional who is in a part-time role leading or supporting one or more Six Sigma improvement projects. A Six Sigma Green Belt is expected to possess in depth understanding of DMAIC and knowledge of application of various Six Sigma tools and techniques.

Six Sigma Black Belt

A Six Sigma Black Belt is a professional who is in a full time Six Sigma role leading improvement projects. A Six Sigma Black Belt is expected to possess excellent knowledge and application experience of Six Sigma concepts and methodology and exceptionally strong in DMAIC as well as various Six Sigma tools.

Six Sigma Master Black Belt

A Six Sigma Master Black Belt is a professional who is an expert in Six Sigma and owns the strategic implementation of Six Sigma across the organisation. A Six Sigma Master Black Belt is expected to possess extensive knowledge and expertise of Six Sigma on top of great leadership qualities. Their responsibilities include overall ownership of Six sigma implementation in the organisation, mentoring other Six Sigma Black Belts, Six Sigma Green Belts, Six Sigma Yellow Belts and Six Sigma teams.

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