BookmarkSubscribeRSS Feed
aska_ujita
Obsidian | Level 7

Hello there, 

 

I am testing two treatments (trained and not trained). And after I collected the behaviour and scored it in 0 (absence of reactivity) and 1 (presence of reactivity). The data were collected in days of lactation (1, 3, 5, 7 and 9 ).

 

Example:

Day of lactation  --->  Percentage of reactivity by group  ---> Significance

Day 1   --->  30% (trained group)  80% (not trained group) ---> P value

Day 3   --->  20% (trained group)  60% (not trained group) ---> P value

Day 5   --->  10% (trained group)  45% (not trained group) ---> P value

Day 7   --->  0% (trained group)  30% (not trained group) ---> P value

Day 9   --->  0% (trained group)  20% (not trained group) ---> P value

Mean   --->  12% (trained group)  47% (not trained group) ---> P value

 

So... I  would like to compare between treatments by day.

 

My datas have non-normal distribution and are binomial.

I used PROC GLIMMIX:

           proc glimmix data=A;
           class treatment day;
           model reactivity=treatment day treatment*day / dist=binomial DDFM=KR;
           random subject subjectID;
           lsmeans treatment/ adjust=tukey lines;
           by day;
           run;

 

But I read some papers that used "Mann–Whitney U test", is there somebody who can explain how to do it?

or just PROC GLIMMIX is already enough?

 

Thank you for the help.

4 REPLIES 4
Norman21
Lapis Lazuli | Level 10

Hi,

 

If you look near the top of this page:

 

https://stats.idre.ucla.edu/sas/whatstat/what-statistical-analysis-should-i-usestatistical-analyses-...

 

(or search for "Wilcoxon-Mann-Whitney", which is another name for the Mann-Whitney U test), you will see an example using SAS.

Norman.
SAS 9.4 (TS1M6) X64_10PRO WIN 10.0.17763 Workstation

aska_ujita
Obsidian | Level 7

Hello Norman21, thank you for replying.

 

I tried the proc, but I have no idea how to interpretate...

 

Sem título.pngHistogram3.png

 

Thank you for your help!!

 

Doc_Duke
Rhodochrosite | Level 12

Aska,

 

You could use the Mann-Whitney-Wilcoxon (MWW) within a day to assess whether the trained or untrained had different reactivity.  As each subject is assessed on each day, it would be inappropriate to simply lump all of the observations into one MWW analysis (violates the independence assumption).

 

As far as interpretation is concerned, this Wiki is reasonable

https://en.wikipedia.org/wiki/Mann%E2%80%93Whitney_U_test

and you can also get a lot from the SAS documentation.

 

I generally use the two-sided t-approximation for the test for the MWW.

 

I've not used GLIMMIX in years, so I can't comment on it's appropriateness.

 

Doc

bikashten
Fluorite | Level 6

   Aska,

i think you can use this code for binomial distribution with repeated measures:

proc glimmix data=A;
	class subjectID treatment day;
	model reactivity=treatment day treatment*day / dist=binomial DDFM=KR;
	random subjectID;
	lsmeans treatment day treatment*day/ pdiff lines;

	 /* if there is a significant interaction then you can compare the treatment effects for each day*/;
	lsmeans treatment*day/sliceby=day pdiff lines;
run;

Thank you,

Bikash

SAS Innovate 2025: Register Now

Registration is now open for SAS Innovate 2025 , our biggest and most exciting global event of the year! Join us in Orlando, FL, May 6-9.
Sign up by Dec. 31 to get the 2024 rate of just $495.
Register now!

What is ANOVA?

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.

Discussion stats
  • 4 replies
  • 1838 views
  • 0 likes
  • 4 in conversation