What is Six Sigma? | Concepts | Principles | Examples

What is Six Sigma?

→ Sigma (𝝈) is the Greek letter representing a statistical unit of measurement that defines the standard deviation (SD) of a population.
→ Six refers to the number of SD’s from the specialized limit to the mean.
→ It measures the variability or spread of the data.
→ 6𝝈 is a highly structured strategy.
→ It is a comprehensive and flexible system for achieving, sustaining, and maximizing business success.
→ It is more about the culture than the tools and all the people who adopted Quality in everything they do.
→ It is people driving improvements based on facts and data and a detailed roadmap of process improvement.
→ It is an initiative that extends and strengthens quality and productivity efforts.
→ The old belief was high quality = high cost but the new belief is high quality = low cost.
→ You can easily understand this concept by the below analysis of cost vs quality

History of Six Sigma:

→ Motorola developed this concept in 1987.
→ It is basically a bunch of various quality tools.
→ One of the most important tools of this methodology is the Control Chart.
→ Control Charts were developed way back in 1924 by quality guru Walter A. Shewhart.
→ Bill Smith of Motorola is considered to be the father of 6𝝈.
→ Mikel Harry was also the Co-founder and he was sometimes referred to as the 'father of 6𝝈'. (source: Wikipedia)
→ Motorola was the first company to receive the Malcolm Baldridge National Quality Award in the year 1988.
→ Looking at the success of 6𝝈 at Motorola number of other companies, such as General Electric, Dow Chemical, DuPont, Honeywell, and Whirlpool adopted this tool.
→ These are some of the early adopters.
→ By adopting this method, many companies have improved their operation, reduce their defects level, and made their customers satisfied.
→ Jack Welch of General Electric has made 6𝝈 more popular around the world.
→ In General Electric, employee promotions were depending on whether the employee had a specific 6𝝈 belt or not.

Milestones:

→ 1986 6𝝈 formulated by Bill Smith in Motorola.
→ 1988 Motorola becomes the first company to win the Malcolm Baldridge National Quality Award.
→ 1993 Allied Signal (Now Honeywell) adopted this methodology.
→ 1995 General Electric (GE) launched the 6𝝈 initiative.
→ 1998 Honeywell adopted this method.

Benefits of Six Sigma Implementation:

→ This Project improves the capability of their business.
→ It increases performance and decreases in variation.
→ Decrease the defect generation.
→ Improve the profit of the organization.
→ This project Improves employee morale and motivation.
→ It improves in quality of products and customer satisfaction.
→ Using the 6𝝈 Methodology, an organization can develop a strategy an implement proper action for revenue and increase, cost reduction, and improvements.
→ 6𝝈 Methodology helps management to create a vision of the organization.
→ It helps to set the benchmark and after sustaining and maintaining the benchmark further improves the benchmark this methodology helps us to continuously improve the system.
→ By 6𝝈 methodology, organizations can set a goal and guide the team to work towards achieving it.
→ It calculates the process performance using its own unit known as 𝝈 unit like our performance is 4𝝈, 5𝝈, etc...
→ It is a robust methodology for problem-solving and improvement.

What is the concept of Six Sigma?

→ It can be understood in three different approaches:

[01] Methodology Approach

→ DMAIC Methodology used for the Improvement Project.
→ DMAIC is a structured problem-solving roadmap and tools.

[02] Philosophy Approach

→ Reduce variation in your process and take customer-focused, data-driven decisions.

[03] Metric Approach

→ 3.4 Defects Per Million Opportunities.
→ DPMO allows you to take the complexity of the product/process into account.
→ Rule of thumb is to consider at least three opportunities for a physical part/component – one for form, one for fit, and one for function, in the absence of better considerations.

What are the 6 Sigma principles?

• Reduce the variation
• Maintain and improve the process at the specified mean
• Eliminating the defects and wastes
• Increase customer satisfaction
• Increase Productivity and Profitability

Why is it called Six Sigma?

→ How many multiple standard deviations fit within each side of the specification limit is the 𝝈 level of the process.
→ The concept of Mean, Central Tendency, and Standard Deviation is the most important to understand the concept of Six Sigma.
→ 01. Mean: It is the arithmetic average of a process data set.
→ 02. Central tendency: It is the tendency of data to be around this mean or average value.
→ 03. Standard Deviation(σ): It's a measure of variation.
→ Higher standard deviation means the value of the data set spread in a wide range.
→ Lower standard deviation means the values of data are near the mean.
→ If the value of 𝝈 is lower then we can fix more 𝝈 between the process average and specification limit so the higher 𝝈 level is good.
 → There are two types of specification limits: (a) Lower Specification Limit (LSL) & (b) Upper Specification Limit (USL)
→ Simply, we can say that the specification limit is the minimum and maximum acceptable limits of the customer's requirement.
→ 𝝈 is the capability of the process, higher the 𝝈 level means to lower the defects, and lower the 𝝈 level means higher the defect.

Meaning of Six Sigma with Examples

Sigma Level vs DPMO [Defects per Million Opportunities] vs Yield %

→ You can easily understand the comparison of 𝝈 Level vs DPMO vs Yield % from the below picture.

→ From the above table, we can easily say that as the 𝝈 level increase the defects decrease.
→ For example, in the 4𝝈 process the defects are 6210 per million opportunities and for 5𝝈 the defects are 230 per million opportunities, and for 6𝝈 the defects are 3.4 per million opportunities.

How Good is Good Enough?

→ 99.9% is already VERY GOOD
→ But what could happen at a quality level of 99.9% (i.e. 1000 ppm)
     Examples:-
    ⇢1 wrong drug prescription per 1000 prescriptions
    ⇢1 brake fail per 1000 newly manufactured car/bike
    ⇢1 airbag does not open per 1000 car
    ⇢1 airplane crash per 1000 ride
    ⇢1 student fail per 1000 student
    ⇢1 person reaches late at theater per 1000 person
→ So to avoid this kind of situation we have to be more accurate and precise

3𝝈 vs 6𝝈 Process

→ You can easily understand the difference between the two processes by referring below picture.

👉 See Also:

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➨ Lean Manufacturing & Top 26 Lean Manufacturing Tools

➨ ISO 9001:2015 & IATF 16949:2016

➨ 7 QC Tools

➨ Quality Core Tools (MSA, FMEA, PPAP, APQP, SPC)

➨ QA & QC Topics