topic Re: How to see "X-bar Chart" for Subgroup Data Without creating "S Chart/R cha in Statistical Procedures

How to see "X-bar Chart" for Subgroup Data Without creating "S Chart/R chart" ?

bhr-q — Fri, 17 May 2024 18:00:40 GMT

Hello, I want to create just Xbar chart for LOS(hours) quartely with 8 subgroups using SAS.,

I used XSCHART , it will give me both both X-bar and S charts together. Same for XR chart.

but I only want to have X-bar chart.

I also cannot use only xchart in my SAS code as xchart is used for individual data not for subgroup data.

How can I adjust my SAS code to see only the X-bar chart in my output?

proc shewhart data=MIS;
xSchart LOS*AdmitYYQ / Markers outtable=outtable ;
run;

Attached is the output to see both are in the same frame.

Thanks

Re: How to see "X-bar Chart" for Subgroup Data Without creating "S Chart/R cha

PaigeMiller — Fri, 17 May 2024 18:40:15 GMT

Use the NOCHART2 option

Re: How to see "X-bar Chart" for Subgroup Data Without creating "S Chart/R cha

Zard — Fri, 17 May 2024 18:41:56 GMT

You can use the NOCHART2 option in the XSCHART or the XRCHART statement to suppress the secondary chart.

proc shewhart data=MIS;
xSchart LOS*AdmitYYQ / Markers outtable=outtable nochart2;
run;

Re: How to see "X-bar Chart" for Subgroup Data Without creating "S Chart/R cha

bhr-q — Fri, 17 May 2024 19:11:22 GMT

Great, Thank you

Re: How to see "X-bar Chart" for Subgroup Data Without creating "S Chart/R cha

Quentin — Sat, 18 May 2024 11:19:08 GMT

@bhr-q wrote:

I also cannot use only xchart in my SAS code as xchart is used for individual data not for subgroup data.

How can I adjust my SAS code to see only the X-bar chart in my output?

nochart2 is a fine solution. You could also use XCHART. XCHART in PROC SHEWHART is for subgroup means, the individual data chart is called an IRCHART.

Re: How to see "X-bar Chart" for Subgroup Data Without creating "S Chart/R cha

bhr-q — Thu, 23 May 2024 13:32:32 GMT

Thank you for the response, I actually tried Xchart, but doesn't work for the subgroup sample size greater than 25. so, I need to use nochart2.

Re: How to see "X-bar Chart" for Subgroup Data Without creating "S Chart/R cha

Quentin — Sat, 25 May 2024 12:14:24 GMT

@bhr-q wrote:
Thank you for the response, I actually tried Xchart, but doesn't work for the subgroup sample size greater than 25. so, I need to use nochart2.

If you use Xchart, by default it uses the subgroup range to estimate the process SD, with sample size greater than 25 you get an error, but it comes with a helpful suggestion:

ERROR: A subgroup sample size greater than 25 was encountered for process variable x.
NOTE: Suggested alternatives are to subdivide the subgroups, or to base the control limits on subgroup standard deviations rather
      than subgroup ranges.
NOTE: Use the STDDEVS option in an XCHART or MCHART statement to specify estimation of the process standard deviation from
      subgroup standard deviations rather than subgroup ranges.

So if you add the STDDEVS option, the XCHART will use subgroup SD to estimate the process SD, which is what an XSCHART does by default.

In my understanding,

xchart y*lot /stddevs ;

is equivalent to:

xschart y*lot /nochart2 ;

So, just two different ways to do the same thing (as often is available in SAS).

Re: How to see "X-bar Chart" for Subgroup Data Without creating "S Chart/R cha

bhr-q — Sun, 26 May 2024 02:31:38 GMT

Thank you so much for letting me know, I did just now, and it works. Great way to know.