What is Six Sigma?
The definition of Six Sigma could vary from the perspective of a company owner to the view of a statistician. A company owner sees six-sigma as a way of improving his business by saving tons of money. And producing excellent quality at the same time. For a statistician six sigma is a way to reduce product variation and keeping the DPMO of 3.4. It means a process is allowed to have only 3.4 defected products in one million units.
Six-Sigma is set of several proven quality techniques and methodologies to achieve almost error-free production. Those who do not know about sigma, sigma is the standard deviation for a specific set of data. Six Sigma requires the process standard deviation be no more than one-twelfth of total allowable spread, means plus and minus six sigma.
Six Sigma graph
Consider the example of the weight of 1 million parts. With a standard deviation of 0.02 and an average weight of 50kg. Then the product weight could vary +0.12kg and -0.12kg from the average weight. It means the weight of product could vary from 49.88kg to 50.12kg. And only 3.4 units are allowed to go out of the limits for a successful measurement of Six Sigma.
The concept of Six-Sigma is not evolved over-night, some of its ideas are more than 100 years old. To see the full history of Six Sigma, check this post here.
Why use six sigma?
A company’s performance measured by the sigma level of their business processes. Most of the companies operate under three to four levels of sigma, which means they are having 66,807 to 6,210 defects per million respectively. On the other side, some industries like pharmaceutical and aerospace are going for seven to eight sigma level because they cannot afford to have even three defects in one million. If one product fails, that could cost somebody’s life and a massive amount of money.
A majority of the tech experts believe that the requirement of exceptionally high quality is limited to long-line manufacturing processes. If all of the industries were using three sigma level, following things would happen:
- 10,800,000 mishandled health claims each year.
- 18,900 lost US savings bond every month.
- Virtually no modern computer would function.
- 4,050 invoices sent out incorrectly each month by a modest-sized telecommunications company.
- 540,000 false call detail records each day from a regional telecommunication company.
- 270 million faulty credit card transactions each year in the US.
So, there is no doubt in going to six sigma and higher level for many industries to achieve almost error-free service (Thomas Pyzdek, 2017).
Six Sigma based on the analogy of DMAIC. D stands for define. M is for measurement. A is for analyzing. I is for improving. And C refers to control. Another famous analogy Is DMADV expressed as design, measure, analyze, design and verify. In define phase, every aspect of the main problem required defining followed by measurement of data. After that, analysis of data and then improvement with control. Six Sigma professionals categorized in the yellow belt, green belt, black belt, master black belt, and champions.
Time to reach six sigma
On average, it takes 2.5 years to a medium-big level manufacturing company to attain the six-sigma level. But it depends on several things like initial sigma level, production, and budget of the company. With the advancement of technology, time for attaining six-sigma level is reducing dramatically.