Re: Calculate Z-Score for non-normal data
Bev D is correct. Just because you can calculate a z-score, which Minitab's non-normal benchmark capability analysis will do, does not mean that you should.
The z-distribution is a standardized, normal distribution with a mean of 0 and a standard deviation of 1. By its very definition, it is not appropriate for non-normal distributions.
A better way is to fit the non-normal distribution and directly calculate the percentages from that distribution. Minitab will do this, and any decent statistical package should do the same. Minitab's non-normal capability will also provide the percentages out of tolerance.