topic Re: Saving Limits for P Chart in Discussions

Saving Limits for P Chart

lucianoa — Sun, 11 Jun 2023 11:18:38 GMT

I am working in JMP 15. And I cannot save the control limits for a P Chart that I generated, because the UCL is different for each "Y."

I need to be able to save the limits for each Y attribute. Is this only possible for I Charts when the UCL is constant?

Re: Saving Limits for P Chart

statman — Mon, 25 Oct 2021 16:54:05 GMT

I'm not exactly sure what you mean by "for each Y"? Do you mean for each sample or are you asking about different reasons for failure? I think you understand the issue, p-charts will have varying control limits because the size of the sample is changing. If you can keep the sample size constant (np charts) then you could get a constant control limit. I MR charts may be useful depending on the proportion of defectives (large proportions).

Re: Saving Limits for P Chart

tonya_mauldin — Mon, 25 Oct 2021 16:58:26 GMT

If you use the Save Summaries option in the red triangle menu, you can see the varying control limits for each point plotted.

Re: Saving Limits for P Chart

lucianoa — Mon, 25 Oct 2021 17:05:28 GMT

Thank you Tonya, this worked. Now my question problem is - how do I apply those limits to a different chart. I used the "Get Limits" function. But I got this error:

This was when I tried to use the data table directly in the format that was put out by "Save Summaries"

Re: Saving Limits for P Chart

tonya_mauldin — Mon, 25 Oct 2021 17:27:04 GMT

The summary data table does not have the proper format for a limits data table. Furthermore, a limits data table only works if the limits are constant. It does not work with non-constant limits. You will need to grab the sigma from the Show Sigma report and then use JSL similar to the following

Control Chart Builder(
	Variables( Y( :NO ), Subgroup( :State ) ),
	Chart(
		Position( 1 ),
		Set Control Limits( {Avg( 0.026 ), Sigma( 0.02 )} ),
	),
	Chart(
		Position( 2 ),
		Set Control Limits( {Avg( 0.02 ), Sigma( 0.0241124109987879 )} )
	)
)

Re: Saving Limits for P Chart

lucianoa — Mon, 25 Oct 2021 17:41:25 GMT

Do you have any idea why the Show Sigma Report would be greyed out, not allowing me to click?

Re: Saving Limits for P Chart

tonya_mauldin — Mon, 25 Oct 2021 17:56:18 GMT

Sorry. I forgot that you had an attribute chart. Show Sigma Report is only available for Variables control charts. Control chart builder has no method of specifying non-constant limits for attribute charts. This can be done with variables charts only.