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Suppose I have a process that I want to calculate the TPY:

Data:

Units (U) = 140 parts

Defectives (D) = 140 parts

**1)**First situation - all parts pass without defects

TPY = (140/140) * 100 = 100% or

TPY = e^(-D/U) * 100 = e^(-0/140) * 100 = 100%

**2)**Second situation - any part pass without defects

TPY = (0/140) * 100 = 0% or

TPY = e^(-D/U) = e^(-140/140) * 100 = 36.79%

I did not understand why the results of item 2 are not the same. Can anyone help me, please ?

I get the TPY formula from Six Sigma Material site.