BookmarkSubscribeRSS Feed
Robin_moon
Fluorite | Level 6

I performed a mmrm model as below:

 

 proc mixed data = have;
         class id treatment week strata;
         model chg = baseline treatment week treatment*week treatment*strata/ ddfm = KR;
         repeated week/ subject = id type = UN;
         lsmeans treatment*week/ cl alpha = 0.05 diff
         ods output Tests3=tests3 lsmeans=lsmeans diffs=diffs;
         run;

In the model:

 

(1) id: represents the patient id, ie 101,102,103....

(2) chg: represents the change from baseline of hba1c

(3) baseline: the value of hba1c at baseline

(4) treatment: contains 2 categories: "drug" and "placebo"

(5) week: contrains 3 levels: week8, week16, week24

(6) strata: represents the stratification by the median of hba1c at baseline, ie:

       group1=patient of those who have hba1c at baseline <= median of hba1c at baseline;

       group2=patient of those who have hba1c at baseline > median of hba1c at baseline.

 

In general, I'd like to test the interaction between strata and treatment, but I am not sure if I performed the test in the right way. Because I checked the results (as below), the column of "Diffs in LS means" were pretty close between strata, however the interaction p-value is statistically significant. (The values of Diffs in LS means were got from the output file diffs, and the p for interaction were got from the output file test3.)

interaction.PNG

I also checked the Diffs in LS means not only at week24, but also week 8 and week16, they all looked pretty close between strata. So did I interpret the data in a wrong way? Or did I perform the model in a wrong way? What data should look different if the p for interaction is significant? Thanks!

Ready to join fellow brilliant minds for the SAS Hackathon?

Build your skills. Make connections. Enjoy creative freedom. Maybe change the world. Registration is now open through August 30th. Visit the SAS Hackathon homepage.

Register today!
How to Concatenate Values

Learn how use the CAT functions in SAS to join values from multiple variables into a single value.

Find more tutorials on the SAS Users YouTube channel.

Click image to register for webinarClick image to register for webinar

Classroom Training Available!

Select SAS Training centers are offering in-person courses. View upcoming courses for:

View all other training opportunities.

Discussion stats
  • 0 replies
  • 372 views
  • 0 likes
  • 1 in conversation