3 by 3 within-subjects setup

[Will Mellick]

Dear SwE users,

I am trying to set up a basic (no covariate) model for a full within-subjects design, including 3 visits/scans (V1, V2 and V3) and 3 treatment conditions (A, B, C), and wanted to ensure I have things correct. I found some earlier posts helpful, but remain a bit confused. Here goes...

First question, when entering the "subjects" do the assigned numbers need to be sequential. For instance, using the example from the SwE manual (attached) but modified to include missing scans, would I enter the subjects as follows:

Visit 1:  1-11 (all cases in sequential order excluding 12 due to no scan)

Visit 2:  1, 3-12 (excluding case 2 due to no scan otherwise, again, in sequential order)

Visit 3: 2-11 (in sequential order, excluding 1 and 12 due to no scans)

In other words, is it ok to omit a given subject ID from one visit (given no data) and then introduce their ID number for a later visit (given data)? Are the subject IDs just unique identifiers and the particular number we assign to a given case doesn't matter?

Second question, for my 3 x 3 design can someone please confirm I have set it up correctly? I entered 9 covariates and denoted their position in the scan order with vectors. The covariates entered were: AV1, AV2, AV3; BV1, BV2, BV3; and CV1, CV2, CV3. This accounts for each combination of condition x visit. Please see attached design matrix for reference.

Please let me know if I can be clearer in anyway and thank you in advance for your support! First timer over here.

Best,

Will