I am confuse the how to calculate the sgima level of process, please tell me below which one is right and which is wrong clearly.
We have 1,000,000 productions, find defect is 8,000. defect opportunity is 1.
Then case 1
DPMO is 8,000 according to the ASQ six sigmal primer appendix, the sigmal level is 2.9 sigma(with 1.5 shift)
DPU is 0.008 DPMO=0.008
Y= RTY= e-DPU=0.992
Probablity of defect is P(d)=1-Y = 1-0.992=0.008
then use Z value table is 2.41
and add 1.5 shift, then the sigma level is 2.41+1.5=3.9 sigmal
using formula sigmal level= 0.8406+ SQRT(29.37-(2.221ln(PPM)))
then 0.846+SQRT(29.37-(2.221ln8000))=3.9 sigmal
the resuult of case 2 and 3 are different with case1 which one is right?
if we want to know the cpk of this process, is 8,000/1,000,000=0.8% just P value(because it is attribute data), that is right?