Six Sigma – Bell Curve

Anoop,
 
While the technical definition for the sigma level of a process is the number of standard deviations that exist between the processes average and the closest of either the upper/lower specification (assuming that we can count of 6 increments before the limit) the projection of the VOP is still the normal curve at +/-3 standard deviations from the average (explaining 99.73% of the expected outcomes).
 
Sigma levels of a process provide a capability assessment and are integrating both VOC and VOP.  Standard deviations are used to portray the expected variation of the process and are a reflection of the VOP.
 
Regards,
Erik  

Dear Eric – Thanks for your note. I think I understand using Sigma as representing process capability and standard deviation explaining variation in the process. The question that I had was that if we look at the bell curve having the mean equivalent to the target, how many standard deviations on either side needs to be fit to depict a Six Sigma process. I understand from Dr. Scott reply that it has to be six standard deviations on both sides (ie, a total of 12 standard deviations). Put another way, if I have the classical bell curve with mean=target, with 3 standard deviations on either side of the mean  with Z=-3 coinciding with the LSL and Z=3 coinciding with the USL, explains a 3 Sigma process and not a Six Sigma process.
Thanks and Regards,
 
Anoop
PS: The reason for posting this question was that I had somebody looking at this classical bell curve and telling me that it represents a 6 Sigma process and my argument was that it represents a 3 Sigma process. I hope with the answers that I got from you and Dr. Scott, my understanding is right!