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What is Six Sigma? (Part 1)
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What is Six Sigma? It is an approach to quality first developed at General Electric that tries to combine the best elements of both the American and Japanese techniques of Quality Assurance.
Most (all?) successful companies are always looking for quality. The tired old saw is - It's cheaper to do it right than do it over. Six Sigma (6 σ) is an approach that has become pretty standard. However i digress.
Sigma (σ) is a Greek letter that is used to denote Standard Deviation. Don't run - it's really a simple concept, in spite of what your college stat prof mumbled about. think about your good old normal distribution. Standard deviation tells us how valid the mean or average is. I refer to it as a "Clumping Factor." If data is tightly clumped around the mean then we might say that the mean is representative of the distribution.
Now as to sigma. 1 Standard deviation +/- a mean covers 68% of the area under the curve. The amount goes up rapidly as the number of standard deviations increases. 6 σ or the average (mean) + or - 6 standard deviations tells us that we are looking at 99.9997% efficiency.
| σ's | % |
| 1 | 31 |
| 2 | 69.2 |
| 3 | 93.3 |
| 4 | 99.379 |
| 5 | 99.977 |
| 6 | 99.9997 |
Source :Wikipedia
Next: OK, Why should I care?
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