Comparing a repeated measures variable and within-subject nested subgroups

Jason2020 — Wed, 18 Sep 2019 21:20:55 GMT

This data set below is part of a larger set for an experiment to compare 2 treatments (GROUP) and the outcome variable is millimeter measurements (DEPTH) made on teeth nested within subjects. The measurements were made at 4 time points (WEEKS), and there are some missing values for DEPTH. Also, although most subjects have 2 treated teeth (one for each treatment), some subjects have more than 2 treated teeth. I would like to fit a repeated measures model to compare the 2 treatment groups, and later I may include other covariates in the model. Is the following model adequate? If not, I would appreciate it if someone would suggest applicable modifications.

Thanks you.

The data set (partial):

Subj Tooth Group Depth Weeks

1 AA A 3 BASELINE

1 AA A 0 6

1 AA A . 12

1 AA A . 24

1 BB B 4 BASELINE

1 BB B 3 6

1 BB B . 12

1 BB B . 24

2 CC B 2 BASELINE

2 CC B 0 6

2 CC B 0 12

2 CC B 0 24

2 AA A 3 BASELINE

2 AA A 0 6

2 AA A 0 12

2 AA A 0 24

2 GG A 5 BASELINE

2 GG A 1 6

2 GG A 1 12

2 GG A 2 24

The proposed model:

PROC MIXED data=long;

Class subj tooth group;

Model depth = group | weeks;

Repeated weeks / subject=tooth(subj) Group=group ;

Run;

Re: Comparing a repeated measures variable and within-subject nested subgroups

Jason2020 — Thu, 19 Sep 2019 13:16:25 GMT

I forgot to mention that subjects are a random sample, teeth are also random term within subjects, and time (WEEKS) is a fixed term.

topic Comparing a repeated measures variable and within-subject nested subgroups in Statistical Procedures

Comparing a repeated measures variable and within-subject nested subgroups

Re: Comparing a repeated measures variable and within-subject nested subgroups