What is the PPM for a 3 sigma level?

The PPM (Parts Per Million) for a 3 sigma level is 66,810. This figure originates from the statistical concept of process capability. Specifically, in a normal distribution, the 3 sigma level indicates a capability that includes about 99.73% of all data points, meaning that approximately 0.27% of data falls outside this range in both tails of the distribution.

To convert this percentage to PPM, we recognize that 0.27% corresponds to 2.7 opportunities out of every 1,000. When expressed in PPM, it translates to 2.7 opportunities out of 1,000,000, which leads to:

[

0.0027 \times 1,000,000 = 2,700 , \text{ppm}

]

However, this figure represents the total defects that occur within the tails, which accumulates and leads to an understanding that for processes operating at a 3 sigma level:

[

\text{PPM} = 66,810

]

This number reflects a significant potential for defects. The understanding of sigma levels provides a framework for evaluating and improving processes, illustrating how many units produced can realistically expect to be defective based