Contrast in PROC MIXED

smortaheb — Wed, 29 May 2019 14:09:29 GMT

Hello,

I have a dataset which has observations before and after a treatment in 2 conditions. So I have "post" and "Pre" treatment measurements in condition "A" and "post" and "pre" treatment measurements in condition "B". I want to compare (Post - Pre) in condition A with (Post - Pre) in condition B. For that, I wrote the following code(time represents pre and post):

PROC MIXED method=REML, data=my_data;

class subj_id condition time gender;

model value = time condition gender time*condition;

random int / subject=subj_id type=UN;

contrast 'my_contrast' time*condition 1 -1 -1 1;

RUN;

Because I am new to SAS, I don't know whether this code does the same thing that I want or not. Can you help me to understand it better. Thanks!

Re: Contrast in PROC MIXED

PaigeMiller — Wed, 29 May 2019 16:44:47 GMT

Use the E option of the contrast statement, this will tell you what is being multiplied by 1 and what is being multiplied by –1.

contrast 'my_contrast' time*condition 1 -1 -1 1/e;

topic Contrast in PROC MIXED in SAS Programming

Contrast in PROC MIXED

Re: Contrast in PROC MIXED