What Is Six Sigma?

I've been talking about Japanese lean manufacturing methods such as Kaizem, Kanban and 5S, but what about Six Sigma? What is Six Sigma?

Six Sigma is a method of improving quality that was developed by Motorola in the 1980's. The term "sigma" is used to indicate variation, and Six Sigma is based on identifying and reducing variation. This can be variation in quality, in process time, in inventory levels, or in costs. Six Sigma uses statistical analysis to identify and correct variations.

There are five parts to Six Sigma represented by the acronym DMAIC:

Define (Identify Projects): Six Sigma starts by identifying a suitable project. Not all businesses and projects are suitable for Six Sigma. Since it is based on statistical analysis, the project must include quantifiable parameters.

Measure (Quantify Current Variation): Look at all aspects of the process to be improved, included related and subprocesses, to identify and quantify all variations.

Analyze: Determine the cause of variations.

Improve: Quantifies the effects of the causes of variations, and identify the maximum allowable range of variation. Establish a calibrated system for measuring deviations of the variables. Once variations can be measured, modify the process to reduce variations to within the acceptable range.

Control (Sustain): Standards, proceedures, training and other tools are used to ensure the modified processs remains within the acceptable range of variance.