Six Sigma stands for Six Standard Deviations (Sigma is the 
Greek letter used to represent standard deviation in 
statistics) from mean. Six Sigma methodology provides the 
techniques and tools to improve the capability and reduce the 
defects in any process.
Six Sigma methodology improves any existing business process 
by constantly reviewing and re-tuning the process.  To achieve 
this, Six Sigma uses a methodology known as DMAIC (Define 
opportunities, Measure performance, Analyze opportunity, 
Improve performance, Control performance).