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Control Chart - Process Capability question

Mark_Zwald

When you use Control Chart Builder with a process variable that has a spec limit property, JMP will also show the capability analysis (very nice). When you add a Phase variable to the control chart, the process capability goes away which is disappointing, and the option to turn on the Process Capability analysis goes away as well from the LRT. So my questions are:

1. Why does the Capability analysis disappear when a Phase variable is added (ie. is there some mathematical justification)?
2. If a phase variable is added, wouldn't it make sense to split the capability analysis by that phase variable rather than disappear it?

This question comes up a lot from our customers and I don't have a good answer for it, so hopefully someone here knows.

Thanks,

Mark

Accepted answers

Mark_Bailey

The idea of splitting the process capability analysis across phases had not occurred before. I checked Jira for related tickets, and I found none. I checked with the CCB developer, who directed me to the process capability developer. The idea is now under consideration.
It makes sense to accommodate a phase variable and split the report. You can use the phase variable in the By role for now.

It was also noted that you can do this analysis via the Process Screening platform, although in that platform, the variable is called grouping and not a phase.

All comments

Mark_Bailey

The idea of splitting the process capability analysis across phases had not occurred before. I checked Jira for related tickets, and I found none. I checked with the CCB developer, who directed me to the process capability developer. The idea is now under consideration.
It makes sense to accommodate a phase variable and split the report. You can use the phase variable in the By role for now.

It was also noted that you can do this analysis via the Process Screening platform, although in that platform, the variable is called grouping and not a phase.

MarilynWheatley

Since what Mark suggested is now under consideration... one of our competitors does this. Their feature does a Before/After capability comparison and provides the control chart and capability summary before and after the change in the process. They also run a couple of t-tests to check if the mean shifted and if the variance was reduced, as well as provide a % reduction is out of spec product (hopefully it was a reduction). That might be useful for some of JMP's users.

Mark_Bailey

Tonya Mauldin was able to find an existing ticket that exactly matches your request. (I missed it.) So we are now reviewing the history of this request and thinking about how best to satisfy it.