Six Sigma is a quality movement methodology which originated in Motorola in 1986. It became popular in the 1990’s when companies such as AlliedSignal and General Electric utilised Six Sigma to deliver their business plans. Jack Welshe, CEO of GE, proclaimed that he wanted six sigma to be “part of the genetic code of our future leadership”.
Six Sigma is focused on eliminating process variation. This result in delivering customer expectations cost effectively. Typically Six Sigma focuses on improving existing processes and essentially has three components. Six Sigma is . . .
- A Philosophy of variation reduction
- A Measurement (Six Sigma)
- A Methodology (DMAIC)
The Philosophy of Six Sigma is to eliminate variation from all business processes. Visually this is described in Figure 1. An everyday example is that of parking your car in the centre of a car park space and to do this consistently every time your park your car. Business examples of variation reduction include reducing cost of scrap from a machine, reducing batch paperwork errors or standardising the recruitment process. Jack Welshe’s passion for six sigma can be viewed on a 2 minute interview.
Figure 1 Philosophy of Variation Reduction
Six Sigma is also a Measurement of process performance. A scale is devised from 0 to 6 (it can go beyond 6) and each level correlates to a certain yield and defect level. Examples of Sigma Scores are tabulated in Table 1. The popular Six Sigma score equates to a yield of 99.9997% or 3.4 defects for every million opportunities.
|
Sigma Score
|
Process Yield
|
No of Defects per Million Opportunities
|
|
1
|
30.9%
|
691,462
|
|
2
|
69.1%
|
308,538
|
|
3
|
93.3%
|
66,807
|
|
4
|
99.38%
|
6,210
|
|
5
|
99.977%
|
233
|
|
6
|
99.99966%
|
3.4
|
Table 1 Sigma Scores and associated yields and defect levels
Table 2 provides a comparison of a 3.8 sigma score and 6 sigma score in our everyday lives. These examples provide the reality of just how important it is to strive for a six sigma. For example, if a hospital surgery is performing at 3.8 sigma, which intuitively is a good yield at 99%, translates into 5,000 incorrect surgeries a week. A 6 sigma score reduces this to less than 2 incorrect surgeries a week.
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3.8 Sigma = 99% Good
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6 Sigma = 99.99966% Good
|
|
5,000 incorrect surgical operations per week
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1.7 incorrect surgical operations per week
|
|
200,000 incorrect drug descriptions per year
|
68 incorrect drug descriptions per year
|
|
2 short or long landings at major airports everyday
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1 short or long landings at major airports every 5 years.
|
|
Unsafe drinking water for almost 15minutes a day
|
Unsafe drinking water for 1 minute in seven months
|
Table 2 Practical examples of Sigma Levels
Six Sigma as a Methodology. For an organisation to achieve Six Sigma, this is a significant achievement. It requires time, resources and a standardised approach to deliver process improvements. To this end, Six Sigma utilises a methodology described by the acronym DMAIC to achieve six sigma. DMAIC is the first letter of each phase of the methodology which is Define, Measure, Analyse, Improve and Control. For each phase, a number of qualitative and quantitative tools are available and these are described in the Six Sigma Tools section. Each phase can be described as follows
- Define – Define the problem and map out the current process
- Measure – Measure current performance and ensure appropriate gauging
- Analyse – Analyse reasons why problem is be occurring and identify root cause
- Improve – Select solutions to eliminate root cause identified
- Control – Sustain the gains made from the Improve Phase
In conclusion, Six Sigma is a philosophy of eliminating variation from all processes to deliver a quality product to customers cost effectively. The measurement used to define this quality level or goal is termed Six Sigma. This equate to a process yield of 99.9997% or 3.4 defects for every million opportunities. To achieve this aggressive goal, the DMAIC methodology will guide you through improvement cycle effectively.