What is Six Sigma – Point 1

Fundamentally, Six Sigma symbolizes a quantitative level of quality that is generally considered to be world-class.

“Sigma” stands for the statistical standard deviation of a set of data, or the measure of the variability of the data, and “Six” represents the number of such standard deviations from the average, or mean, for a normal distribution of data. Think “bell curve”. The more standard deviations you move away from the average, the less chance there is of finding any data (like fewer ‘A+’ grades than the average ‘C’s in school). When applied to the topic of quality, this concept can be used to estimate the capability of a process and the probability of the existence of a defect in a product or service.

The more standard deviations that fit within the specification limits for a process, the lower the probability of a defect and the higher the level of quality. Therefore, a Three Sigma (3 standard deviations) process reflects lower quality than a Six Sigma one, which is 99.99966% accurate and results in less than 3.4 defects per million opportunities of making a defect.

Posted by Bill Robinson