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" <fis...@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
>>
>>
>>
>>
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