Dear Doug,

Thank you very much for your help. Unfortunately, I'm still confused about these questions...First, I wanted to see the correlation between cortical thickness and BIS (an impulsivity-test), corrected for age and gender. Therefore, I chose this question : "Does the correlation between thickness and BIS-total, accounting for gender, differ from zero. Nuisance factor: age". 
Is that wrong...?

Then, I wanted to look at the differences in this correlation between males and females. Therefore, I chose:  "Does the thickness-BIS-correlation differ between 0 and 1?"  (male and female....yes I have to change the numbers ind male and female!)

I read the qdec- tutorial and found  "....Does the Thickness--age correlation differ between male and female?... Click on this question to display the statistically significant regions where the age and thickness correlation are different in men and women..." (http://surfer.nmr.mgh.harvard.edu/fswiki/FsTutorial/QdecGroupAnalysis). 

And that would be what I try to find. I want to see if females and males have differences in the thickness-BIS-correlation. And I do not understand why qdec displays negative and positive values for this question. And if this question only mean the correlation (without the correction for age..?), I wonder how to see gender differences.

Could you explain me how to see the gender differences?

Thank you!

Leni







Am 22.04.2013 um 15:56 schrieb Douglas N Greve <greve@nmr.mgh.harvard.edu>:

Hi Lena, it is not a difference, it is a correlation between thickness
and BIS. The sentence produced by QDEC would be clearer if you gave the
groups actual names instead of 0 and 1.
doug



On 04/22/2013 04:46 AM, Hélène Bretschneider wrote:
Dear freesurfers,
I want to look at the gender differences of a correlation between cortical thickness and some impulsivity-tests.
When I use qdec, the question "Does the thickness-BIS-correlation differ between 0 and 1?"  is displayed. So, 0 and 1 are female/male. But there are positive and negative correlations (red and blue voxels)...what does it mean? There can not be a negative difference...??
Thank you very much!
Leni


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