How to calculate group*session Interaction in Rest or DPABI?

Submitted by yaosir on Tue, 03/03/2015 - 10:57

Dear Chao-Gan,

My experiment is mixed-factor design, with group (3 levels) as a between-group factor, and session (2 levels, pre- and post-intervention) as a within-group factor. I am not only interested in the main effects but also the interaction between group and session. Someone suggest me to use the flexible factorial design in SPM to calculate the main effects of session and the group*session interaction, and use the full factorial design to calculate the main effects of group. Still, I wonder if I can calculate the group*session Interaction in Rest or DPABI?

Thank you in advance!

Best,

Vincent

Forums:

YAN Chao-Gan

Fri, 03/06/2015 - 02:29

Hi Vincent,
DPABI or REST doesn't have a factorial design module yet. I suggest you to use SPM at the current stage.

Best,

Chao-Gan



O

yaosir

Fri, 03/06/2015 - 12:17

Hi Chao-Gan,

Thank you for your reply. Since I am not familiar with SPM (relative to Rest and DPABI), I still have some questions about the flexible factorial design.

My design matrix is as follows:

factor 1=subject (61 subjects), factor 2=group (3 groups, 25/17/19 subjects in group 1/2/3 respectively), factor 3 = session (pre- and post-intervention)

F contrast vector for the main effect of session= zeros(1,3) [1 -1] [25/61 -25/61] [17/61 -17/61] [19/61 -19/61] zeros(1,61)

F contrast vextor for the group*session interaction= zeros(1,3) zeros(1,2) [-1 1] [0 0] [1 -1] zeros(1,61)

I am not sure if the contrast vectors are right, since I adopted them from Glascher and Gitelman's paper, which was based on only 2 groups.

Thank you in advance.

Vincent