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The Six Sigma Quality Method
 
 

What is Six Sigma?

Six Sigma is a measurement of quality. It is achieved when a process works correctly 99.99966% of the time. This equates to just 3.4 errors per million, which is about as good as any human endeavour can achieve. 

To be more precise, Six Sigma is a statistical measure of standard deviations within a process. However, that is not a helpful way to explain it to a newcomer to the subject.

Many organisations have Six Sigma initiatives. These use the necessary Six Sigma philosophy and methods to work towards raising the quality level to 99.99966% accuracy (Six Sigma).

Sigma Defects Per Million Successes Defects
One Sigma 690,000 31.0% 69.0%
Two Sigma 308,537 69.1% 30.9%
Three Sigma 66,807 93.3% 6.7%
Four Sigma 6,210 99.4% 0.6%
Five Sigma 233 99.97% 0.03%
Six Sigma 3.4 99.99966% 0.00034%

The Six Sigma Philosophy.

Central to the Six Sigma philosophy is the understanding of what process needs to be measured. This is often referred to as Critical to Customer (CTC). This highlights which business units need to become actively involved in the Six Sigma initiative. 

Six Sigma evolved in a manufacturing environment, but it can be applied equally to other types of organisation. For instance, a bank may decide that it needs to achieve at least Six Sigma accuracy when moving customer's money between accounts, because that is exactly what their customers expect. 

The Five Steps of Six Sigma.

Every Six Sigma project covers 5 basic steps, which are normally known by the acronym DMAIC (which is made up of the initial letters of each step):
 

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Key managers and senior staff members need to be trained to an appropriate level; yellow belt, green belt, black belt or master black belt.

Why Implement Six Sigma?

The business case for adopting a Six Sigma approach can be significantly boosted by taking into account the present hidden cost of correcting errors. In a manufacturing environment this could include such items as the wages bill while staff stand idle due to a shortage of materials, the cost of sending people around the world to correct manufacturing faults in items that have been shipped overseas, the cost of returning incorrect items shipped to customers and the loss of revenue (and profits) when a customer transfers their business to a more reliable supplier. 

Complex processes tend by their nature to go across departmental boundaries, so one of the first challenges when aiming for Six Sigma is to ensure that everyone is committed to the idea and that no department sets internal targets which would prevent success. 

A real-life example of a short-sighted departmental target was in a computer company where the manufacturing department wanted to reduce the cost of administration. Their solution was to employ fewer order administrators and target them to make fewer changes to each customer order. The administration staff prevaricated in some very creative ways when customers wanted their orders to be changed and customers were lost because the  company was hard to do business with.

Criticism of Six Sigma.

Six Sigma does have its critics. Some say that it is a group of existing techniques which have simply been brought together under one headline. That is true. But surely it doesn't detract from what it can achieve. Indeed, it is helpful to have a "buzz term" such as Six Sigma which everyone in an organisation can be familiar with.

The other main objection is a technical one, to the effect that Six Sigma methods fail to take into account the fact that real life processes do not generate statistics which fit exactly onto a standard deviation curve. That is true. But Six Sigma methods do approximate to real life and are practical to implement.

Six Sigma in One Sentence.

Six Sigma is a philosophy of continuous improvement, it is a set of tools for Improving quality and it is a statistical measure of how well a process works. 

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