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

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, 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 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

Hi Greve, Thanks for your help. I have 28 females and 26 males in one group. If it is necessary to take gender and eTIV as a covariate, I don't know how to take them as covariate in SPSS. Subcortical volume can be divided by eTIV, but for gender, I don't know how to do. And the mean age of female and male don't have statistical significance (p=0.362).In this case, is it possible to ignore the effect of gender?

Sincerely, Zheng

At 2017-12-05 01:39:55, "Douglas N Greve" greve@nmr.mgh.harvard.edu wrote:

Yes, you should take those into account. Not sure what you mean by "which stat analysis".

On 12/01/2017 07:50 PM, 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 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

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