help > RE: How to write design matrix and contrast for continuous variable analysis (not comparison between groups)
Jul 20, 2021  11:07 PM | Andrew Zalesky
RE: How to write design matrix and contrast for continuous variable analysis (not comparison between groups)
Hi Qiushi,

This kind of design should be straightforward. You would simply include a column with the age of each subject, and two additional columns for sex and FD. An additional column containing all 1's may also be needed. That's it. The contrast would be [1 0 0 0] or [-1 0 0 0] and select "t-test".

Yes the value in the threshold box is a t-statistic (or F-statistic in the case of the F-test). Your calculations seem correct.

Yes the significance box is for the the component, not for the edge.

best,

Andrew

Originally posted by Qiushi Wang:
Hello everyone,
I have checked the manual and the forum posts, as I am not doing comparison between groups or longitudinal analysis ( I do continuous variable analysis use cross-sectional data), so I am a little confused about the writing of design matrix and contrast.
I used a set of cross-sectional data to explore which edges in the FC matrix had significant age effects. Specifically:
I have a group of subjects with different ages (suppose 5 people), and I want to examine which edges develop significantly with age (subjects are not divided in to groups but put together). Meanwhile, sex and FD are used as covariates. How should I write design matrix and contrast?
In addition, I have two simple questions and I'm not so confident about: (1) Dose the value filled in the “Threshold” box a T statistic? For example, if I have 5 subjects and I want to identify the significant edges at p=0.01, according to df=5 and p=0.01, 4.032 should be filled in here. If I want p=0.001 as the significance level for the edges, then 6.869? (2) Does the value filled in the "Significance" box correspond to the P value of the Component (not the P value for the edge)?
Thank you very much!

Best wishes
Qiushi