I don't follow the two examples you have there. Why are you reporting a map of Cohen's d?
On 11/21/2013 09:40 AM, cj wrote:
Dear doug: Thank you for your reply ,and it looks good now.But I meet a question when I am ready to write in my paper,that is how to decribe the annotation of my effect size maps ,I found two papers that were described as follows: 1、Cohen‘s d for the difference between two means was based on sex and age corrected means from a general linear model fitted at each vertex across the cortical surface. 2、The figures present cortical maps of effect sizes (Cohen’s d) based on age-adjusted means from general linear model analyses. Is this right? and which one is better?and is there any cite for it ?and how to describe the pooled standard deviation in the Cohen'd equation,should I write and the pooled standard deviation was based on the residual error standard deviation from the general linear model analyses follow the above two description? Look forward for your answer and thanks a lot! Ji Chen
在 2013-11-08 02:29:38，"Douglas N Greve" <greve@nmr.mgh.harvard.edu mailto:greve@nmr.mgh.harvard.edu> 写道：
I think the gamma/rstd what you want. doug
On 11/07/2013 08:14 AM, 陈骥 wrote:
Dear freesurfer experts
In qdec I use the DODS degsin to obtain the thickness difference
between my two groups with age ,gender as nuisance.Then I want to get the effect size map instead of report the significance level. In freesurfer wiki I found that we can obtain the effect size map via gamma/sqrt(gammavar*Npilot), where Npilot is the number subjects in the pilot study.While I have two groups,one control group with 25 subjects and one patient group with 25 subjects too,I doubt that which number I should use ,the number of patient group subjects 25 or for the whole subjects across groups 50 to repalce the Npilot in the equation? And then I look for previous relevant topic in the freesurfer mail list, found that doug suggested that we can get the effect size just use gamma/rstd, I tried for that but found completely different result between I use the equation of gamma/sqrt(gammavar*Npilot), which equation should I use for I want to get the Cohen'd effect size map? Thank you in advance for your helps! Ji Chen
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