Good point, so I'll re-phrase my second sentence to read:
I ask this because there isn't an example on this subject in JMP Help.
A case study would be helpful to explain two things that aren't clear to me: Upper/Lower Margin and Difference to Detect.
It ain't what you don't know that gets you in trouble, it's what you know for sure that just ain't so. (Attributed to Mark Twain)