Cauchy distribution. Where is Process capability button?

[#1]

Why where is no Process Capability button? Or you can't do it with Cauchy's distribution data.

[#2]

Sorry... Why is there no process capability button?

[#3 · Accepted solution]

According to the JMP Documentation, the Cauchy distribution has an undefined Mean and Standard Deviation. Based upon that, I assume JMP does not have Cp and Cpk for that distribution and thus no need for the button.

[#4]

Yes, but then how do I calculate PPK? Should I take the nearest distribution, if it is? Or should I calculate PPK using Standard Deviation? I need to evaluate the process with nonnormal data distribution.

[#5]

Have you tried fitting all the Distributions, and then determine which have a significant Goodness Of Fit?  You could then use that distribution for your Cp and Cpk

[#6]

yes I click Fit all

And recieve only three, where Cauchy has a priority.

[#7]

Check out the other fits.....they might give you good estimates

[#8]

but goodness of fit points to Cauchy

[#9]

Actually, the mean of the Cauchy distribution is defined but not the higher moments. So, no variance, no standard deviation. No standard deviation, no Ppk.

[#10]

And, just as an aside, if you're responsible for improving a process that outputs data that are really Cauchy distributed, you might want to update your resume...