What is Six Sigma (6σ)?

Six Sigma is a quality-control methodology developed by American engineer Bill Smith while working at Motorola in 1986. The method uses data-driven analysis to limit mistakes or defects in a corporate or business process. The six sigma system is a method to work faster with fewer mistakes.

Nowadays, Six Sigma has developed into a more general business-management viewpoint, focused on meeting customer requirements, improving customer retention, and improving and sustaining products and services. Six Sigma applies to all types of industries. Many companies, including Motorola itself, offer Six Sigma training with special certifications carrying the names of white belt, yellow belt, green belt, and black belt.

Six Sigma methods look for improving manufacturing quality by identifying and eliminating the causes of defects and minimizing variance in manufacturing and business processes. Six Sigma does it by using experimental and statistical quality control management methods and by hiring Six Sigma experts. Each Six Sigma project follows a defined method and has specific quality targets, such as reducing pollution or increasing customer experience.



What you are going to learn?

    Understanding of Six Sigma
    Six Sigma Methodologies
    Download What is Six Sigma PDF
    What are the key principles of Six Sigma?
        1. Focus on the Customer
        2. Use data
        3. Improve continuously
        4. Involve people
        5. Flexible and responsive work environment
    Six Sigma Levels or Six Sigma Certification
        Six Sigma White Belts
        Six Sigma Yellow Belts
        Six Sigma Green Belts
        Six Sigma Black Belt
        Six Sigma Master Black Belt
    How to implement Six Sigma
    What is the importance of Six Sigma?


Understanding of Six Sigma

In statistical analysis, the Greek letter sigma (σ) is used to stand for a standard deviation from the mean. It is basically a statistical benchmark all business tries to achieve. The business process, which is achieving six sigma produces less than 3.4 defects per 1 million parts, is considered efficient.

Let's understand six sigma by this figure:


This straight line is the mean line, represents by µ= 0. The horizontal axis showing distance from the mean, denoted by the units of standard deviation which is represented as Sigma (σ). The upper and lower specification limits (USL and LSL) are at a distance of 6σ from the mean.

Even if the mean line were to move right or left by 1.5 standard deviations or 1.5 sigma, there will be still a safety cushion. If your process is behaving between 6 sigma, that means your upper and lower specification limit is on 6 sigma, then you will be able to produce less than 3.4 defects per 1 million parts, which is almost perfect and achievable in actual condition.



If I make a comparison between Three Sigma (3σ) and Six Sigma (6σ), we can see defects per million is 66,807 in the case of 3 sigma, and defects per million is only 3.4 with 6 sigma.




Six Sigma Methodologies

Six Sigma projects follow two project methodologies,

    Six Sigma DMAIC, &
    Six Sigma DMADV.

It derived each word of the name from the major steps in its process, but each has its own use.

Let's breakdown Six Sigma DMAIC step-by-step:

    Define: Define the system. Identify the project objectives and all consumer deliverables.
    Measure: Measure key aspects of the current process, and understand performance.
    Analyze: Analyze the data to investigate and verify cause and effect of the differences. Determine root causes of any defects.
    Improve: Improve the current process based upon data analysis using techniques such as design of experiments, mistake proofing, and standard work to establish a new, future state process. Establish ways to eliminate defects and correct the process.
    Control: Control the future state process to ensure that they correct any deviations from the target before they result in defects. Manage future process performance.

We should use the DMAIC methodology when an existing product or service is not meeting customer needs or performing to its highest standards. It is used to correct an existing process.

Here is a step-by-step breakdown of Six Sigma DMADV:

The first three steps are identical to DMAIC.

    Define: Define the system. Identify the project objectives and all consumer deliverables.
    Measure: Measure key aspects of the current process, and understand performance.
    Analyze: Analyze the data to investigate and verify cause and effect of the differences. Determine root causes of any defects.
    Design: Design an improved alternative, create a process that meets customer needs and expectations.
    Verify: Verify the design, ensure process designed meets customer needs and performs adequately.

The DMADV methodology should be used when a business is developing a new product or service, or when using DMAIC for a current project or process fails.

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