On Tue, Jul 24, 2018 at 10:10 AM, Martin Juneja <mj70481@gmail.com> wrote:

Hi Dr. Greve,

So I checked both. The rstd.mgh files are very similar in both cases (with and without ICV as covariate), but gamma.mgh files are very different for both cases. Here I am attaching screen shot for both cases:

Gamma_With_ICV as covariate and Gamma_Without_ICV as covariate.

Could you please have a look at the attached screen shots and provide your thoughts/interpretation of this comparison?

Thanks.

On Tue, Jul 24, 2018 at 9:35 AM, Douglas N. Greve <dgreve@mgh.harvard.edu> wrote:

For noise compare the values in the rstd.mgh file, for effect size look
in the gamma.mgh file

On 07/24/2018 12:27 PM, Martin Juneja wrote:
>
> External Email - Use Caution
>
> Hi Dr. Greve,
>
> Thanks for your quick reply. Could you please give me more details how
> can I check this whether its because of noise or its because of less
> CV difference?
> I am not sure what method/way is the best and commonly used to confirm
> these factors.
>
> Thanks.
>
> On Tue, Jul 24, 2018 at 7:06 AM, Douglas Greve <dgreve@mgh.harvard.edu

> <mailto:dgreve@mgh.harvard.edu>> wrote:
>
> your results could have vanished after ICV correction for one of
> two reasons: the CV difference became less or the values became
> noisier (or a combination). So check in your data which one of
> those things happened.
>
>
> On 7/23/18 8:30 PM, Martin Juneja wrote:
>>
>> External Email - Use Caution
>>
>> Hello experts,
>>
>> I am interested in identifying regions of interest by comparing
>> cortical volume (CV) between controls and patients.
>>
>> After including age and sex as my covariates, I identified
>> regions X1 and X2, which showed significantly lower CV for
>> patients (as compared to controls).
>>
>> But after I include ICV as another covariate, my results show
>> that for none of the areas there is any significant difference in
>> CV, i.e. my results vanish.
>>
>> When I checked subjectwise ICV for each group, I found that there
>> is almost significant difference (two-sampled t-test, p = 0.067)
>> in ICV between two groups, but interestingly mean group ICV for
>> patients group was larger compared than mean ICV for controls.
>> But as I said earlier, regions X1 and X2 had significantly lower
>> CV for patients (as compared to controls), when I didn't include
>> ICV as covariate.
>>
>> Could you please help me in interpreting these results? Is there
>> any advice regarding inclusion of ICV as covariate? Or my results
>> are purely because of differences in ICV between groups, and
>> there is no real findings regarding the regions identified (X1
>> and X2)?
>>
>> Thanks a lot !
>>
>>
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