Hi Ed,

yes - your design matrix will throw a rank deficient warning. 

You would need to remove the main effect that is not changing between follow up measures. For example, if age group remains the same, logitudinal data is not needed to measure the main effect of age group. Check out some of the other posts on the forum where this issue is discussed in more detail. 

Another option is to move to a full-blown LME model in which individuals are modeled as random effects but that is not supported by NBS due to the computational burden of LME models. 

Andrew

Originally posted by Ed Hutchings:

Hello,

Just getting in touch regarding my design matrix for a 2x2 mixed anova with few repeat measures. I understand I can’t use exchange blocks here, and my current design matrix (attached) has columns for age group, sex, age*sex, and each subject.

When I run the contrast [1 0 0 0…] to assess main effect of age group, I get a rank deficiency error. Please let me know what I’m doing wrong! Thanks for your time.

Best,

Ed