Hi Jon, Yes, this is all fine. There's no need to demean age and sex in this case, but doing so won't hurt either. All the best, Anderson On 14 August 2016 at 03:11, Jon Anderson <[log in to unmask]> wrote: > Dear FSL experts, > I want to build design matrix and contrast for my TBSS data so I can use > it in the command "randomise". The data is FA maps ( for 50 subjects) and > the design model is for three groups and two covariates ( one > continuous-AGE and the second one categorical-gender). > > Regarding design.mat ( the example bellow is just for 9 subjects and 3 > groups for illustration purposes) > > Group EV1 EV2 EV3 EV4 EV5 > input1 1 1 0 0 > input2 1 1 0 0 > input3 1 1 0 0 > input4 1 0 1 0 > input5 1 0 1 0 > input6 1 0 1 0 > input7 1 0 0 1 > input8 1 0 0 1 > input9 1 0 0 1 > . > . > > > EV1, EV2 EV3 are the groups 1 , 2, 3 > EV4 demeaned age > EV5 demeaned gender ( male =1, female=2) > > The contrasts are > EV1>EV2 1 -1 0 0 0 > EV2>EV3 0 1 -1 0 0 > EV1>EV3 1 0 -1 0 0 > positive EV4 effect 0 0 0 1 0 > negative EV4 effect 0 0 0 -1 0 > positive EV5 effect 0 0 0 01 > negative EV5 effect 0 0 0 0 -1 > > > Kindly is this model correct? > I highly appreciate your help! > > Jon >