Great - and this would be true for all models? For example, in the attached graph, I'm looking at a region representing increased cortical thickness for one group compared to the other (orange blob, Q: "Does the average thickness differ between HC and SAD?" nuisance factor: mean thickness). From this plot it appears that SAD > HC, but based on your answer to the previous question I would think this region should represent HC > SAD. Can you please explain this?
Thank you!
On Wed, Oct 30, 2013 at 7:33 AM, Douglas N Greve
<gr...@nmr.mgh.harvard.edu>wrote:
>
> In your case you have HC listed first, so red/yellow means HC>SAD, blue
> means SAD>HC
> doug
>
>
>
>
>
>
> On 10/29/2013 11:03 PM, Ashley Shurick wrote:
>
>> Hi Doug,
>>
>> Apologies, but I have a rather easy follow-up question that I can't
>> figure out:
>>
>> How do you interpret the effect in each significant region? A previous
>> post suggests using ctrl + left mouse click on a blob and examining the
>> plot of the data. However, for the model I am looking at ("Does the
>> thickness-ERQ correlation differ between HC and SAD?") I still can't
>> determine if cortical thinning represents HC<SAD or SAD<HC. I'm attaching a
>> representative plot here.
>>
>> Thank you,
>>
>> Ashley
>>
>>
>> On Tue, Oct 29, 2013 at 10:25 AM, Ashley Shurick <
>> ashley.shur...@gmail.com
>> <mailto:ashley.shurick@gmail.**com<ashley.shur...@gmail.com>>>
>> wrote:
>>
>> Thank you!
>>
>>
>> On Tue, Oct 29, 2013 at 10:19 AM, Douglas N Greve
>> <gr...@nmr.mgh.harvard.edu
>> <mailto:gr...@nmr.mgh.harvard.**edu<gr...@nmr.mgh.harvard.edu>>>
>> wrote:
>>
>>
>> On 10/29/2013 01:10 PM, Ashley Shurick wrote:
>> > Hi all,
>> >
>> > I'm running analyses in Qdec and want to verify a few things:
>> >
>> > 1. When comparing two groups (HC vs patients) I am including
>> mean
>> > cortical thickness as a covariate, using the following equation:
>> >
>> >
>> > bh.thickness = (lh.thickness*lh.surfarea +
>> rh.thickness*rh.surfarea) /
>> > (lh.surfarea + rh.surfarea)
>> >
>> >
>> > Is this the best way to calculate global mean thickness?
>> Yes
>> >
>> >
>> > 2. I want to regress out any effects of age, therefore I need to
>> > demean the ages for my groups as a whole, and not perform this
>> > calculation on each group separately, correct?
>> Yes, in which case the test of the difference between groups
>> will be
>> done at an age equal to the mean of the ages.
>> >
>> > 3. I'm including questionnaires as a covariate of interest -
>> do I need
>> > to demean these values as well?
>> When you do a test on a continuous covariate, that test will be
>> unaffected by demeaning of the covariate. Demeaning will
>> affect the
>> difference between groups if you use a separate covariate for each
>> group. If you have a single covariate across groups, demeaning
>> will have
>> no effect.
>>
>> doug
>> >
>> >
>> > Thank you in advance for your help!
>> >
>> >
>> > Ashley
>> >
>> >
>> > --
>> > Ashley A. Shurick
>> > Ph.D. Candidate
>> > Department of Psychology
>> > Stanford University
>> >
>> >
>> > ______________________________**_________________
>> > Freesurfer mailing list
>> > Freesurfer@nmr.mgh.harvard.edu
>>
>> <mailto:freesur...@nmr.mgh.**harvard.edu<Freesurfer@nmr.mgh.harvard.edu>
>> >
>>
>> > https://mail.nmr.mgh.harvard.**edu/mailman/listinfo/**
>> freesurfer <https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer>
>>
>> --
>> Douglas N. Greve, Ph.D.
>> MGH-NMR Center
>> gr...@nmr.mgh.harvard.edu
>> <mailto:gr...@nmr.mgh.harvard.**edu<gr...@nmr.mgh.harvard.edu>
>> >
>> Phone Number: 617-724-2358 <tel:617-724-2358>
>> Fax: 617-726-7422 <tel:617-726-7422>
>>
>> Bugs:
>> surfer.nmr.mgh.harvard.edu/**fswiki/BugReporting<http://surfer.nmr.mgh.harvard.edu/fswiki/BugReporting>
>>
>> <http://surfer.nmr.mgh.**harvard.edu/fswiki/**BugReporting<http://surfer.nmr.mgh.harvard.edu/fswiki/BugReporting>
>> >
>> FileDrop:
>> https://gate.nmr.mgh.harvard.**edu/filedrop2<https://gate.nmr.mgh.harvard.edu/filedrop2>
>>
>> www.nmr.mgh.harvard.edu/**facility/filedrop/index.html<http://www.nmr.mgh.harvard.edu/facility/filedrop/index.html>
>>
>> <http://www.nmr.mgh.harvard.**edu/facility/filedrop/index.**html<http://www.nmr.mgh.harvard.edu/facility/filedrop/index.html>
>> >
>>
>> Outgoing:
>> ftp://surfer.nmr.mgh.harvard.**edu/transfer/outgoing/flat/**
>> greve/ <ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/>
>>
>> ______________________________**_________________
>> Freesurfer mailing list
>> Freesurfer@nmr.mgh.harvard.edu
>>
>> <mailto:freesur...@nmr.mgh.**harvard.edu<Freesurfer@nmr.mgh.harvard.edu>
>> >
>>
>>
>> https://mail.nmr.mgh.harvard.**edu/mailman/listinfo/**freesurfer<https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer>
>>
>>
>> The information in this e-mail is intended only for the person
>> to whom it is
>> addressed. If you believe this e-mail was sent to you in error
>> and the e-mail
>> contains patient information, please contact the Partners
>> Compliance HelpLine at
>>
>> http://www.partners.org/**complianceline<http://www.partners.org/complianceline>.
>> If the e-mail was
>> sent to you in error
>> but does not contain patient information, please contact the
>> sender and properly
>> dispose of the e-mail.
>>
>>
>>
>>
> --
> Douglas N. Greve, Ph.D.
> MGH-NMR Center
> gr...@nmr.mgh.harvard.edu
> Phone Number: 617-724-2358
> Fax: 617-726-7422
>
> Bugs:
> surfer.nmr.mgh.harvard.edu/**fswiki/BugReporting<http://surfer.nmr.mgh.harvard.edu/fswiki/BugReporting>
> FileDrop:
> https://gate.nmr.mgh.harvard.**edu/filedrop2<https://gate.nmr.mgh.harvard.edu/filedrop2>
> www.nmr.mgh.harvard.edu/**facility/filedrop/index.html<http://www.nmr.mgh.harvard.edu/facility/filedrop/index.html>
> Outgoing: ftp://surfer.nmr.mgh.harvard.**edu/transfer/outgoing/flat/**
> greve/ <ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/>
>
>
<<attachment: Screen shot 2013-10-30 at 8.19.25 AM.png>>
_______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer The information in this e-mail is intended only for the person to whom it is addressed. If you believe this e-mail was sent to you in error and the e-mail contains patient information, please contact the Partners Compliance HelpLine at http://www.partners.org/complianceline . If the e-mail was sent to you in error but does not contain patient information, please contact the sender and properly dispose of the e-mail.
