
64 Quality management for organizations using Lean Six Sigma techniques
As products designs became more complex and defective products were becoming
more prevalent, customers started demanding higher quality. Three-sigma quality for each
OFD was no longer acceptable.
For example, consider a product that contains 1000 OFDs. If, for each OFD, three-sigma
quality levels are achieved, only about 5% of the products would be defect free.
The calculation used to obtain this probability requires raising the fraction conform-
ing (0.997) to the power of 1000, and is based on the binomial probability distribution
(Devore 2000).
Assuming 1000 OFDs, only 3