Dear Douglas,

 

Thank you so much for your answer!

 

Sorry, but I don't think I explained myself correctly in the previous email.

 

I want to analyze the difference in cortical thickness between two groups (CU and CI), adjusting for a covariate (cortisol CSF) and the interaction between them.

 

So my model would be: cortical thickness ~ diagnosis + CSF cortisol + diagnosis*CSF cortisol

 

Using the GLM DODS, the contrasts, according to the wiki example (MailScanner has detected a possible fraud attempt from "secure-web.cisco.com" claiming to be https://surfer.nmr.mgh.harvard.edu/fswiki/Fsgdf2G1V), would be:

 

• To verify if only the diagnosis regression coefficient is significant (diagnosis changes cortical thickness regardless of cortisol):

• 1 -1 0 0

• 
  

• To verify if the regression coefficient of the interaction between diagnosis and cortisol is significant (the two change cortical thickness dependently):

• 0 0 1 -1

• 
  

• To verify if only the cortisol regression coefficient is significant (cortisol changes cortical thickness regardless of diagnosis):

• 0 0 0.5 0.5

 

Are these contrasts corret to represent the model we designed?