he last twelve installments have dealt with Lean, now we begin a close look at Six Sigma. First we need to understand that Six Sigma is not one thing, but rather three things:
Six Sigma and Performance Measurements
- Performance Measurements
- Six Sigma Quality
- Six Sigma Methods
At the foundation of Six Sigma is a common way to measure things. Most problems or projects have variables that can be measured. If measurement is possible, then profound knowledge can follow. Data derived from measurements can be viewed using the standard deviation to assess variation. The standard deviation is the common metric in most Six Sigma Projects. Determining the number of standard deviations between the process specifications or project entitlement establishes a common language. This language can be monitored to determine current state and progress towards the future state.
Six Sigma Quality
This is the very ambitious strategy of managing a process to the point that six standard deviations of variation can occur between the process average and the nearest specification limit. In theory, this delivers a process so robust that the probability of defects occurring is no more the 3.4 parts per million. Further examination of this strategy allows the process average to move about within plus and minus 1.5 standard deviations of the average. This now places 4.5 standard deviation between the average and the nearest specification limit. At this point the mathematics will work out to 3.4 PPM.
Six Sigma Methods
In order to achieve Six Sigma levels of quality the folks at Motorola organized a set of problem solving tools referred to DMAIC. This is a most exhaustive and step-by-step method to solve a problem or complete a project. Most of the ingredients in DMAIC have been around for a long time, but have never been organized in such a manner. The power of DMAIC is following a proven road map to success. Many companies have discovered that DMAIC can be effectively used to prosecute many types of projects and it is not limited to just achieving Six Sigma Quality Levels. Many of the projects necessary to create a Lean Enterprise benefit greatly from using DMAIC.
Next issue we will start looking closely at these proven methods, beginning with DMAIC.