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troubles with saving control chart--"control chart sigma" becomes "specified sigma"

unknown

New user here, previously used Minitab.

I'm having a strange issue where, after I generate an IR chart with process capabilities calculated and I save the report, when I reopen the report later on, "control chart sigma" becomes "specified sigma." Moreover, the control limits on the control chart are somewhat different from before the save event. If I try saving to a journal I get the same problem. Anyone seen this before? Am I doing something wrong? My JMP version is 9.0.0.

Thank you!

Patrick

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unknown

Hi patlu,

Thanks for spotting this. I was able to reproduce the title problem when saving the report. JMP development team will fix this for the coming release of JMP. I also wanted to let you know a workaround. You can double click the title and type 'Control Chart Sigma in there. From my observation, there was no problem on the control limits themselves.

Thanks,

Jong-Seok Lee

swelish

I am using JMP 11 and it seems to me the above issue has not been resolved. I my script for an IR chart and capability analysis to use the Control Chart Sigma but it saves a Specified Sigma instead.

Regards

Sean

Jeff_Perkinson

Hi Sean,

When saving a script there is sometimes a natural tension between wanting to save a script that reproduces the results, exactly as you saw them, and saving a script that reproduces the analysis, which may have different results depending on the data.

In the case of the Capability analysis in the Control Chart platform we're trying to meet both of those requirements, sort of.

The computed Control Chart sigma gets saved in the script so that the capability analysis is using the same parameters each time it's run. If you would rather use a computed Control Chart sigma when the script is run, simply edit the script to remove the Sigma() specification in the Capability section.

Control Chart(

Group Size( 1 ),

KSigma( 3 ),

Chart Col(

:DIAMETER,

Individual Measurement,

Moving Range,

Capability(

Distribution(

Continuous Distribution(

Column( :DIAMETER ),

Quantiles( 0 ),

Summary Statistics( 0 ),

Outlier Box Plot( 0 ),

Normal Quantile Plot( 1 ),

Capability Analysis(

LSL( 5 ),

USL( 3.7 ),

Target( 4.2 ),

Sigma( 0.265048929559034 ) // Remove this line to use the Sigma calculated from the control chart

)

);

swelish

Hi Jeff

Deleting the Sigma() specification in the Capability script removes the Specified Sigma capability statistics but does not replace it with the Control Chart Sigma capability statistics. Only the Long Term Sigma (Pp, Ppk) statistics remain. Ideally I would like to be able to display both the Ppk and Cpk.

Thanks!

Sean