I think you probably should since you don't want whatever you find to only reflect differences in head size
cheers Bruce On Sat, 2 Dec 2017, 郑凤莲 wrote:
Hi Bruce,
I think I get it. I have 27 males and 28 females and 26 males. It isn't necessary to corrected by eTIV. Is it right?
Thanks a lot ! Zheng
At 2017-12-02 11:45:10, "Bruce Fischl" fischl@nmr.mgh.harvard.edu wrote:
Hi Zheng
For volume, usually including eTIV reduces the variance and increases power more than you lose for having one additional regressor. Not sure about gender - how unbalanced is your sample? You might be ok with just eTIV Bruce
On Sat, 2 Dec 2017, 郑凤莲 wrote:
Hi professor,
I am using Freesurfer 6.0 and get the volume of subcortical structures. I want to get the relationship between age a
nd
volume. I only have one group, is it necessary to take gender and eTIV as a covariate? If it is necessary, Which statistical analysis should be used? I really appreciate your help. Thanks a lot.
Sincerely, Zheng