Six Sigma

     The term six Sigma is a statistical term that means 3.4 defects per million output or put it in simple words the process is 99.9 9966 person accurate

     Six Sigma helps the companies to focus on developing and delivering near perfect product and services.


     It is corporate quality program that emphasizes in identifying and avoiding valuation.


     The basic approach of six Sigma is to measure performance of an existing process, compare it with statistically valid ideal and find out how to eliminate any variation.

     Six Sigma process involve following five basic steps,

     1 the six Sigma team identifies CTQ's (critical to quality characteristics)  that  customer  feel to have most impact on the quality. It also helps in identifying those factors that are critical for the improvement of the quality.

     2 DTM identifies those key process that influence CTQ's.  And team measures the defect currently generated related to these process

     3 the team identifies the reasons for the defective units generated by identifying brewsky variables that are most likely to create the process variation

     4 the team develops a system for measuring deviation. And the team modified the process so that outputwill be within the acceptable range.

     5. the final step is to see that this key variables remain within the maximum acceptable range over the period of time






     If standard deviation is equal to  (1/6)th of the specification limit then process is said to be six Sigma process

     If specification limit = ± 6σ, then process is said to be six sigma process


     In short, to getting six sigma process we have to maintain standard deviation 1/6 th of the specification limit

     Highest six sigma mens lower defects

Sigma and non conformance Per million when process is centered

Specification Limit	Percent Conformance	Percent Defective	Deffect per million	Process Capability
1σ	68.7	31.3	313000	0.33
2σ	95.45	4.55	45500	0.67
3σ	99.73	0.27	2700	1
4σ	99.9937	0.0063	63	1.33
5σ	99.999943	0.000057	0.57	1.67
6σ	99.9999998	0.0000002	0.002	2
7σ	99.99999998	0.000000019	0.00019	2.33

 

Sigma and non conformance per million Output when process is shifted to ± 1.5σ

Specification Limit	Percent Conformance	Percent Defective	Deffect per million	Process Capability
1σ	30.23	69.77	697700	-0.167
2σ	69.13	30.87	308700	0.167
3σ	93.32	6.68	66800	0.5
4σ	99.379	0.621	6210	0.834
5σ	99.9767	0.0233	233	1.167
6σ	99.99966	0.00034	3.400	1.5

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