Original message
| Mo
 |  "Hi I'm curious"
, Thu 26 Oct 18:49 
Whats the History of the name six sigma in detail. Can you put it into context for me please?
Thanks,
Mo
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Replies:
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| cadams@adamssixsigma.com
| "Re(1):Hi I'm curious" , Fri 27 Oct 08:26
Six Sigma started with Motorola and was the qulaity program tehy used to win the Baldridge Award. How they came up with Six Sigma I do not know.
Six Sigma is accepted as 3.4 ppm defects or less. Yet if you look up 6 sigma in a normal curve it is 2 ppb(parts per billion ) for a double sided test. This is becasue six sigma allows the mean to shift 1.5 standard deviations.
The easy way to make the conversion from defect level to sigma level is to look up in a table. If you want to do your own table. Convert the ppm to a decimal form. Get a single sided Standardized Normal Curve Table. Find your decimal in the body of the table and read the z value. This is generally accepted as the 1.5 SD shifted value. Therefore to get the sigma quality level add 1.5 to the z value. You can check your work with the table following.
Going the other direction given a sigma quality level subtract 1.5 for the shift. Use this as the z value for the Standardized Normal Curve Table and look up the value in the body of the table, that will be the error rate in decimal form. You will have to convert it to ppm.
ppm= sigma level:
3.4ppm =6.0 sigma:
31.7ppm =5.5 sigma:
232.7ppm =5.0 sigma:
1350ppm =4.5 sigma:
6210ppm =4.0 sigma:
22,750ppm =3.5 sigma:
66,811ppm =3.0 sigma:
158,687ppm =2.5 sigma:
308,770ppm =2.0 sigma:
500,000ppm =1.5 sigma:
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