Meritphase|What is Six Sigma and why is it important?

Meritphase|What is Six Sigma and why is it important?

Meritphase - Simply put, Six Sigma is an approach to reduce variation (and consequently reduce defects) in a process to the extent that it produces less than 3.4 defects per million opportunities.

Let us say we are manufacturing soft drinks. Ideally, every bottle should have exactly 750 ml in it. This is the ideal scenario which is most often not true since some variation always exists. So we decide a range, say 748 to 752 ml. If volume of the liquid in the bottle exceeds this range, we consider it to be defective.

Before we move forward, there are a few things about statistics we need to know. Every process can be denoted by two parameters: Mean and Standard Deviation.

Mean shows the central value (average) of the data and Standard Deviation (denoted by Greek letter sigma σ) shows variation in the data from the mean. Higher the σ, higher the variation in the data from the mean.

Now in order to achieve six sigma level, we must reduce the standard deviation to the extent that the difference between the process mean and either limit of the range is more than six times the standard deviation. Since standard deviation is denoted by the Greek letter sigma (σ), this concept became known as Six Sigma

In our soft drinks example, we can say that the process mean is 750 ml. The range is 748 to 752 ml. If it were a six sigma process, the difference between 750 and each limit (748–750=-2 and 752–750=2) should be more than six times σ i.e. σ should be one sixth of 2, which is 0.33 ml.

This means that if the standard deviation of the process is reduced to 0.33, the process will produce less than 3.4 defective pieces in a million bottles produced.

Industries normally use this figure as a target and try to achieve it through various data-driven approaches. The most well-known approach is the DMAIC Approach, which stands for Define-Measure-Analyze-Improve-Control.