First many thanks for the incredible job done here. This is my first post, but this forum already helped many times before today...

I know the question of process capability for one sided tolerance characteristics was discussed before (maybe more than once). However, there is still something bothering me that I can't figure out. It's not only about how to calculate the capability though...

The following are my personal conclusions, so please correct me if I am wrong:

There are two types of characteristics with one sided tolerance:

1- With natural "limit": for example perpendicularity or flatness. These cannot have a value less than 0 and therefore have only the upper tolerance. These characteristics should follow a

**folded normal distribution. Right?**

2- Without natural "limit", but rather with only one actual specification: for example tensile strength which should not be less than X MPa (lower tolerance), but that can go up to whatever value possible. These characteristics should follow a

**normal distribution, right?**Or is there any other specific distribution for these cases (one sided normal distribution for example)?

Is the Cpk calculated the same way in both cases anyway? And is the calculation based on the same dispersion used for normal distribution (3*sigma)?

Once again, thanks for the great job.

Uchiha