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XXXX replied to the topic process performance using non normal data in the forum General 16 years, 2 months ago
Hi Pradeep
You can group the data and then you can find the process capability.
Grouping size should be atleast 4.
Grouping means averaging the values.
After grouping see whether the data is normal if not find the distribution it follows.
Even after if it doesn’t follow any distribution, increase the grouping size.
Usually as you increase…[Read more] -
XXXX replied to the topic sigma levels and central limit theorem in the forum General 16 years, 2 months ago
Hi Mike
If your process produces 68.27 defect free product out of 100, you are at 1 sigma level
Similarly if your process produces 95.45 defect free product out of 100, you are at 2 sigma level, similarly it proceeds.
This is the percentages you have written there.
The formula to calculate sigma level are as follows.
If your data is…[Read more]