Re: Process Capability - How much percentage of tolerance?
It's 60%. The inverse of the index gives the proportion of the tolerance 'consumed' by the process. If you look at the formula you will see that it is a measure of the tolerance divided by a measure of the process spread. So 1/1.67 = .6. Which is 60%
But remember the Xpk indices include the SD of the process AND the location of the process average in relation to the tolerances.