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Six Sigma is a highly disciplined methodology that helps organizations to develop and deliver near perfect processes. We provide some insights into the Six Sigma approach to continuous improvement in this article.
Process Perfect
Six Sigma takes a results-oriented, data-driven approach to eliminating defects in a product or service process. Its name comes from the Greek letter ‘sigma’, which is used as a statistical term to measure how far a process deviates from perfection (‘standards deviation’).
The central idea behind Six Sigma is that if you can measure the number of defects in a process, you can systematically determine how to eliminate them and get as close to zero defects as possible.
The term ‘Six Sigma’ refers to a status that a process must achieve to be considered acceptable. In any one million opportunities for a defect to occur, a process must not produce more than 3.4 defects. If it produces more than this, the process is considered less than perfect and is examined to see where improvements can be made.
Six Sigma Sub-Methodologies
The fundamental objective of a Six Sigma project is to implement measurement-based strategies that focus on process improvement and defect reduction. This is carried out using two Six Sigma sub-methodologies: DMAIC and DMADV.
Both sub-methodologies are similar in that they are both data-driven solutions, relying on facts derived using the measurement systems that are in place. (No decisions in Six Sigma are based on intuition.) However, they are both used for different purposes.
1. DMAIC [1]
The DMAIC methodology is used when an existing process is not meeting expectations. It stands for:
- Define the project goals and (internal and external) customer deliverables
- Measure the process to determine current performance.
- Analyze and determine the root cause(s) of defects
- Improve the process by eliminating defects
- Control future process performance
2. DMADV
The DMADV [2] methodology is used when a process is not yet in existence and there is a need for it to be developed. It stands for:
- Define the project goals and (internal and external) customer deliverables
- Measure and determine customer needs and specifications
- Analyze the process options to meet customer needs
- Design in detail the process to meet customer needs
- Verify the design performance and ability to meet customer needs
Occasionally, DMADV is used to examine an existing process if it has already been looked at (possibly using the DMAIC method) and it is still not considered acceptable.
The Financial Link
A distinct difference between Six Sigma and other continuous improvement approaches is its link to an organization’s finances. The financial benefits of process improvements are quantified and used to help select future projects. Although this is probably true of other approaches, it is a fundamental part of the Six Sigma methodology.
These financial benefits are re-evaluated during the ‘Analyze’ phases to confirm that the cost of the proposed improvements will be supported by the end result. They are then given a final verification during the ‘Control’ phase for DMAIC projects, and the ‘Verify’ phase for those using the DMADV method.
The effort made to link Six Sigma projects to finances has the following benefits:
- The entire organization is connected by Six Sigma as they look to it to make cost savings and increase revenue through improved levels of productivity.
- It helps to differentiate significant process improvement projects from those that are less substantial.
Six Sigma Champions
For any Six Sigma project to be a success, the following roles must be assigned to ensure it is implemented correctly:
- Quality leader. The quality leader ensures that Six Sigma is implemented in an integrated way throughout the organization. It is their responsibility to represent the needs of the customer, and they are normally part of the senior management team.
- Master black belt. Normally assigned to a specific function or department, master black belts work to ensure that quality objectives and targets are set, plans are established, progress is monitored and all necessary training and communication needs are met. They devote their time entirely to Six Sigma projects.
- Process owner. The process owner works closely with the master black belt. They are in charge of specific processes, and monitor and evaluate the tasks and activities established by the master black belt.
- Black belt. Often considered the heart and soul of Six Sigma projects. They work under master black belts to ensure that projects comply with the methodology. Their primary focus is project execution, whereas the master black belts are more concerned with identifying potential projects. Like master black belts, however, they work solely on Six Sigma projects.
- Green belt. These are employees who work on Six Sigma projects, as well as performing their regular job responsibilities. They operate under the guidance of black belts and support them in achieving their objectives.
As with any continuous improvement initiative, senior management must create the conditions for Six Sigma to succeed. They should empower the role holders with the freedom and resources to explore new ideas for breakthrough improvements.
Critical to Quality
‘Critical to quality’ is a term that is frequently used in Six Sigma projects. Essentially, it is what a customer expects from a product or service. For example, ‘I expect my product to be repaired within three days.’ The main objective of those working on a project is to take what is often a qualitative (spoken or written) piece of data and turn this into a quantitative (numerical) piece so that it can be measured.
Numbers Aren’t Everything
While it is the case that Six Sigma often uses complicated statistical tools, its focus is still on serving the best needs of the customer. At its core, it is a systematic approach to problem-solving, and basic data-gathering tools are often all that is required to successfully complete projects.
Further Information
If you are looking to implement Six Sigma in your organization, the following books may help you:
Getting Started in Six Sigma, Michael C Thomsett, John Wiley and Sons Inc, 2004
Provides a thorough introduction to Six Sigma, giving lots of practical and easy to understand advice on how it can be applied in organizations.
The Lean Six Sigma Pocket Toolbook: A Quick Reference to 70 Tools for Improving Quality and Speed, John Maxey, David Rowland, Michael L George, Malcolm Upton, McGraw-Hill Publishing Company, 2004
A list of various tools that can be used as part of all stages of a Six Sigma project.
The Six Sigma Handbook: A Complete Guide for Green Belts, Black Belts and Managers at all Levels, Thomas Pyzdek, McGraw-Hill Publishing Company, 2002
This book provides a more comprehensive guide to Six Sigma, and should be read once you have a good general understanding of its concept.
References[1] Kinney, L. (2023).
DMAIC: The Five Steps to Process Improvement Success [online]. ISixSigma. Available
here. [Accessed 11 August 2023.]
[2] Feldman, K. (2023).
DMADV: The Methodology for Redesigning Boken Processes [online]. ISixSigma. Available
here. [Accessed 11 August 2023.]
ProcessSuccessMethodology for [online]Available here. [Accessed 11 August 2023.]
