Hi Bruce,

For subcortical volume, gender is not as a covariate(28 femaless and 26 males). Then, is it necessary to take gender as a covariate for cortical thickness, volume and surface area in qdec?  

Sincerely,
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, Ö£·ïÁ« 
>wrote:
>
>> Hi professor,
>> 
>>    I am using Freesurfer 6.0 and get the volume of subcortical structures. I want to get the relationship between age and
>> 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
>> 
>> 
>> 
>>