topic Re: proc mixed to get mean and SE in New SAS User

proc mixed to get mean and SE

lc7033907 — Fri, 12 Mar 2021 17:22:30 GMT

Hello all,

I want to use sashelp.class as an example to get mean and SE (standard error) values of height by proc mixed and I like to save these values in a dataset. I found all the SE values are the exactly the same. This is my first time to touch proc mixed, so I really get confused. Anyone can give me some explanation? Thanks.

proc mixed data=sashelp.class(where=(Age in (14,15)));
  class Sex  Age;
  model Height = Sex  Age;
    lsmeans Sex  Age;
run;

Here is output:

Re: proc mixed to get mean and SE

PaigeMiller — Fri, 12 Mar 2021 17:49:52 GMT

I think that's what is supposed to happen with the SE when you estimate some type of linear model for the two-way ANOVA case, and there are equal number of observations in each cell.

Re: proc mixed to get mean and SE

lc7033907 — Fri, 12 Mar 2021 21:27:19 GMT

Hi @PaigeMiller , anyway to correct it, because I guess those numbers should not be equal. Thanks.

Re: proc mixed to get mean and SE

PaigeMiller — Fri, 12 Mar 2021 22:19:22 GMT

@lc7033907 wrote:

Hi @PaigeMiller , anyway to correct it, because I guess those numbers should not be equal. Thanks.

You are incorrect. The SE numbers should be equal in this example.

Re: proc mixed to get mean and SE

lc7033907 — Sat, 13 Mar 2021 04:32:09 GMT

@PaigeMiller Thank you. Now let me modify my real problem and I hope to get some hints. The following is data that I have

data have;
input subjid $2.   Avisitc $3-10 trt $ CHG;
datalines;
1 week 12 A 3.7
1 week 16 A 4.8
2 week 12 B -2
2 week 16 B -2.2
3 week 12 A -3
3 week 16 A -2.5
4 week 12 B 2.8
4 week 16 B 3.0
5 week 12 A 7.0
5 week 16 A 7.1
6 week 12 B 6.4
6 week 16 B 6.8
7 week 12 A -5
7 week 16 A -5.4
8 week 12 B 10
8 week 16 B 11
9 week 12 B -6.4
9 week 16 B -7.1
10 week 12 A 6.3
10 week 16 A 6.9
;

I want to get a report in the following:

Now I have trouble on the last column, because I never use proc mixed before. Any hints are appreciated. Thanks.

Re: proc mixed to get mean and SE

PaigeMiller — Sat, 13 Mar 2021 12:35:54 GMT

You can get most of this from PROC MIXED

ods select lsmeans;
proc mixed data=have;
    class avisitc trt;
    model chg = avisitc*trt;
    lsmeans avisitc*trt;
run;
quit;

If it has to be displayed EXACTLY as shown, then that is a job for other PROCs, and I would recommend you start another thread to discuss how to display results exactly in the desired report form.

Re: proc mixed to get mean and SE

lc7033907 — Sat, 13 Mar 2021 16:33:35 GMT

Thank you so much @PaigeMiller . Your code is exactly the same as what I did on my own. Since I got the same values on SE, I thought I was wrong. Thank you once again.