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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 (https://secure-web.cisco.com/1PUyQNFnXt6UhBGwXfB_vPfCTd6uW7Jf3dH3GiO0aIPFHha...), 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?
Thank you so much again!
Best regards,
Laura Willers de Souza
Master Student in Biochemistry
Zimmer Lab - Federal University of Rio Grande do Sul
- Porto Alegre/RS - Brazil