Hello -
I am analyzing my data with ProcGlimmix and the LSMeans statement, with the Lines command for letter separation. I am writing about the statistical analysis I am doing, and realized I don't know what model that the Lines command uses to determine separation (Fishers, Bonferroni, Tukey, etc.) I've included the code, although I don't think it's necessary.
Does anyone know what test is used, and what source I can use to cite that? I have been looking all over but haven't been able to find a straight answer. Thank you so much!
proc glimmix data=Bruise nobound plots=studentpanel;
class cls Inoc bruise Rep ;
model wcorr = cls|bruise|inoc /dist=n ddfm=kr;
random rep;
lsmeans cls|bruise /pdiff lines cl;
run;
I did not know off the top of my head. So did I do? I read the documentation.
It says:
Yes, that's kind of small, but if you click on it, it becomes readable.
Thanks Paige, but I am specifically asking about the Lines letters separation within LS Means. I could not find that in the documentation at all.
I'm not great with PROC GLIMMIX. Someone like @SteveDenham is probably a better choice. I assume you've read the doc for the LINES option.
If you do not use the ADJUST= option, you get all pairwise least squares mean differences and their significance. The unadjusted p-values are from a statistic that is assumed to have a t distribution. Since you specified DDFM=KR, the test statistic is the one specified in the doc. If you have access to Westfall, Tobias, and Wolfinger (2011, 2nd Ed), they discuss the LINES option and p-values on pp 280-281. (If you specify an ADJUST= option, the p-values are adjusted.)
I'd like to suggest that the table that the LINES option creates is a poor way to visualize the pairwise significance of the differences. For a discussion, see "Graphs for multiple comparisons of means: The lines plot." You can use the PLOTS= option on the LSMEANS statement to request a better visualization. My favorite visualization is PLOTS=DIFFOGRAM, which creates a faithful representation of the significant differences.
Are you ready for the spotlight? We're accepting content ideas for SAS Innovate 2025 to be held May 6-9 in Orlando, FL. The call is open until September 25. Read more here about why you should contribute and what is in it for you!
ANOVA, or Analysis Of Variance, is used to compare the averages or means of two or more populations to better understand how they differ. Watch this tutorial for more.
Find more tutorials on the SAS Users YouTube channel.