dear sir

why we are talking about six sigma and not for seven sigma.

regards
Anil Gupta

Dear Anil

 

Six Sigma processes are fairly accurate (99.997% accurate, 3.4 DPMO). Achieving that level of accuracy itself is very difficult and systematic approach is required apart from capital investment. But if you want to improve the process further to seven or eight sigma level it increases the cost of the process drastically to achieve little more accuracy. Even though, some of the aerospace company has now started talking about seven sigma levels but most of the organizations feels that up to Six Sigma is good enough.

 

Rest, it is more about having business sense. At some places, they may be happy with 2 Sigma or 3 Sigma as well where as at some organizations, no defect is acceptable.

 

So it is about business impact that it makes.

7 sigma takes a lot of efforts, cost to achieve.. this huge cost is not justified by the output... hence 7 sigma is not aspired for...

The simple answer is this - Six Sigma was originally called so because it symbolized the mission at Motorola when they started with the methodology. There is nothing magical about number 6. If we consider accidents during the landing of an aircraft, a 6 sigma performance is not an acceptable performance level anywhere in the world. If an airline is at 6 sigma performance level for this defect definition, it will aspire to reach 12 sigma performance or more. The tools and techniques used in Six Sigma methodology are the same as those used for achieving Zero Defect performance level.

 

Nowadays, some companies call the methodology as Lean Sigma and not Lean Six Sigma. This enables them to focus on targeting performance levels that make business sense and to move away from the number game completely.