That 3.4 ppm defects with "six sigma" is based on allowance of the process
mean shifting by 1.5 sigma. Without the allowance, six sigma would actually
be less than 1 ppm. The numbers without that process mean shift allowance
are:

Cp             x-sigma              total outside two-sided spec. limits
0.5                1.5                                   13.36%
0.67                2                                     4.55%
1                    3                                        0.3%
1.33              4                                         64 ppm
1.63              4.9                                       1 ppm
2                    6                                          0
figures from Juran Quality Handbook, 5th Ed. Table 22.4

Timothy Reeves
ECD Circuit Board Division
13626 South Freeman Road
Mulino, OR 97042
[log in to unmask]
(503) 829-9108 (800) 228-8198  FAX (503) 829-5482



> ----------
> From:         Hollandsworth, Ron
> Sent:         Tuesday, February 8, 2000 5:40 AM
> Subject:      Subj:  Six Sigma
>
> Good Morning TechNetters!
> Here is a brain teaser for this early morning.  Thinking six sigma.  Six
> sigma is suppose to be 3.4 PPM.  Good!  Now what is five sigma, four,
> three,
> two , one.  There is a chart that shows that relationship of a certain
> sigma
> and the PPM associated with that particular sigma value.
>
> Ok, the first five to get the right answer will be eligible to go on to
> the
> "Who wants to be a Black Belt" show.  Enough levity, can someone help me
> out.  Do you know the chart I am referring to?  Can you send me the values
> and I'll make a chart.
>
> Grasshopper Ron
>

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