Published on Apr 02, 2024
The term "Six Sigma" relates to the number of mathematical defects in a process. Six Sigma practitioners focus on systematically eliminating the defects so they can get as close to "zero defects" as possible.
Most people are familiar with the methodological expression of Six Sigma, DMAIC - Define, Measure, Analyze, Improve and Control. Some companies add a R for "recognize" in front of Define and an R for "realize" after Control. You first have to Recognize you have a problem before defining it and, after implementing a solution you have to control it over time to Realize its financial benefits.
While Six Sigma follows the DMAIC methodology at the project level, it follows a well established deployment methodology at the business level. Companies like GE and DuPont have paved the way for making Six Sigma deployable through large networks of Champions, Black Belts, Green Belts, Yellow Belts and Process Owners.
Six Sigma provides a systematic way of improving business processes based on customer needs and factual analysis of company processes. Business intelligence (BI) is technology devoted to accessing, analyzing, and sharing business information.
Organizations like General Electric are combining these two technologies in the form of Six Sigma intelligence, a framework for using information technology to pick Six Sigma projects, get results more efficiently, and ensure their long-term success.
Specifically, BI systems from companies such as Business Objects help organization-wide implementation of Six Sigma in the following ways:
1.More Effective Preparation
2.Faster Implementations
3.Increased Long-Term Success
Six Sigma is one type of methodology adopted by organizations looking to improve performance. Enterprise performance management (EPM) solutions enable you to align people, processes and technologies around common plans to execute and optimize business strategy.
Six Sigma: A process capability in which variability is reduced so that 6 standard deviations fit between the process mean and the specification limits.
Process: A process is a collection of activities that takes one or more kinds of input and creates output that is of value to the customer.
CTQ: CTQ is Critical to Quality. A product feature or process step that must be controlled to guarantee that you deliver what the customer wants.
Defect (D): Any non-conformities in a process or product.
Unit (N): A process step where each unit must be observable and countable with a definite starting and stopping point
Opportunity (O): An opportunity is a product or process characteristic that adds or subtracts value from the product. To be quantifiable, each opportunity must be independent. Thus opportunity is event which can be measured that provides a chance of not meeting a customer requirement.
Normal Distribution: A bell-shaped curve showing a frequency distribution which often occurs in nature.
Mean: The average of measured data.
Process Capability [5]: A measure of the ability of a process to produce an error-free product, by comparing the variability of the process with the variability acceptable to the customer.
Its can also be defined as a measure in “Standard Deviation Units (Z)” of how far the process mean is from the performance standard. How far (in standard deviation units) is the mean from the specification (Lines A+B)
The essence of Six Sigma methodology lies in understanding the customer requirements and aligning with the larger goals also known as the Big Y or business Y. The figure below shows a traditional approach of a vendor. It sees only a part of the customer’s requirements and hence fails to see its bigger picture.
Y = f(X1, X2 ….Xn) where,
Y is key output metrics that are aligned with the strategic goals/objectives of the business. Big Ys provide a direct measure of business performance
X is any parameters that influence the Y
Hence it is very important to understand our customers. The following questions can be asked to help better understand our customers.
1. What does my customer need from our process?
2. How is our process performance from the customer perspective?
3. How does my customer measure my process?
4. How does my customer view my process?
5. How would my customer like for our process to perform?
The first step of any six sigma project is to come out with the customer issues or problem areas also called as VOC (Voice of Customer) in Six Sigma terms. Next these VOCs are mapped to the actual customer CTQs. This is done through a VOC to CTQ translation matrix. Finally we should be able to translate this CTQ into a technical requirements document also referred to as the Voice of the Engineer. The example below would help in understanding the process.
Next define Defect Opportunities
Look for defects in Products or Services
Arrive at DPMO value
Convert DPMO to Process Sigma (Using the Sigma table)
Once the above steps are done one needs to determine whether it’s going to be a software process improvement or a new software process design. Assuming the fact that most of the changes required by customers are to do with process improvement we discuss further the Six Sigma methodology called as DMAIC.
The Six Sigma process consists of five phases: define, measure, analyze, improve, and control. [5]
In this step we define the problem statement and the goal statement. We understand what is the scope of project? What is the defect? Here the project scope and defects are also defined. A business case is made to obtain project approval. Team charter is established with a clear goal statement
A. Identify Project CTQs
B. Develop Team Charter
C. Define Process Map
Six Sigma quality means attaining a business-wide standard of making fewer than 3.4 mistakes per million opportunities to make a mistake. This quality standard includes design, manufacturing, marketing, administration, service, support–all facets of the business. Everyone has the same quality goal and essentially the same method to reach it. While the application to engine design and manufacturing is obvious, the goal of Six Sigma performance–and most of the same tools–also apply to the softer, more administrative processes as well.
After the improvement project has been clearly defined and bounded, the first element in the process of quality improvement is the measurement of performance. Effective measurement demands taking a statistical view of all processes and all problems. This reliance on data and logic is crucial to the pursuit of Six Sigma quality.
The next step is knowing what to measure. The determination of sigma level is essentially based on counting defects, so we must measure the frequency of defects.
Mistakes or defects in a manufacturing process tend to be relatively easy to define–simply a failure to meet a specification. To broaden the application to other processes and to further improve manufacturing, a new definition is helpful: a defect is any failure to meet a customer satisfaction requirement, and the customer is always the next person in the process.
In this beginning phase, you would select the critical-to-quality characteristics you plan to improve. These would be based on an analysis of your customer’s requirements–(usually using a tool like Quality Function Deployment.) After you clearly define your performance standards and validate your measurement system (with gage reliability and repeatability studies), you would then be able to determine short-term and long-term process capability and actual process performance (Cp and Cpk).
The second step is to define performance objectives and identify the sources of process variation. As a business, we have set Six Sigma performance of all processes within five years as our objective. This must be translated into specific objectives in each operation and process.
To identify sources of variation, after counting the defects we must determine when, where and how they occur. Many tools can be used to identify the causes of the variation that creates defects. These include tools that many people have seen before (process mapping, Pareto charts, fishbone diagrams, histograms, scatter diagrams, run charts) and some that may be new (affinity diagrams, box-and-whisker diagrams, multivariate analysis, hypothesis testing).
This phase involves screening for potential causes of variation and discovering interrelationships between them. (The tool commonly used in this phase is Design of Experiment or DOE.) Understanding these complex interrelationships then allows the setting of individual process tolerances that interact to produce the desired result.
In the Control Phase, the process of validating the measurement system and evaluating capability is repeated to insure that improvement occurred. Steps are then taken to control the improved processes. (Some examples of tools used in this phase are statistical process control, mistake proofing and internal quality audits.)
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