[Freesurfer] averaging timecourses

Hi Freesurfer experts

I have extracted the time course of a task fMRI data in a specific contrast and within a specific ROI, in 7 subjects. Consider my specific ROI has 1200 voxels and I extracted the time course for a duration of 5 TRs. After extracting the timecourse, I have a matrix of 1200x5 for each subject. To calculate the average timecourse, I concatenated the matrices for the 7 subjects and made one matrix of 8400x5. Then I averaged across columns which gives me one mean per column. I also calculated the standard error for each column. My question is if this voxel wise way of averaging and calculating the standard error is statistically correct or not. I deeply appreciate any comments on this.

Thanks a lot Mona