Process capability:
What is the observed performance in Minitab?
The formula minitab uses helps anwer the question:
For
i) Observed Performance PPM < LSL = 1,000,000 * ((number of observations < LSL) / n)
ii) Observed Performance PPM > USL = 1,000,000 * ((number of observations > USL) / n)
Observed Performance Total = sum of (i) and (ii)