On 28/04/2012, at 12:24 AM, MCLAREN, Donald wrote:
> (1) If you include a column for each subject in a one-sample t-test,
> then the group effect will always have a t-statistic of Inf. This
> results from the residual being 0. As far as I know, this was never
> done in SPM5.
>
> (2) I do not have a strong opinion on this, except to say that your
> contrast will no longer be comparing TaskA v. TaskB or TaskA v.
> baseline. Rather, you will be comparing the globally-adjusted
> contrast.
>
> (3) What subject-specific are you referring to?
>
> From the wording in your email, it seems like you might be using
> multiple measurements per subject. In this case, you should not be
> using a one-sample t-test.
>
> Best Regards, Donald McLaren
> =================
> D.G. McLaren, Ph.D.
> Postdoctoral Research Fellow, GRECC, Bedford VA
> Research Fellow, Department of Neurology, Massachusetts General Hospital and
> Harvard Medical School
> Website:
http://www.martinos.org/~mclaren
> Office:
(773) 406-2464
> =====================
> This e-mail contains CONFIDENTIAL INFORMATION which may contain PROTECTED
> HEALTHCARE INFORMATION and may also be LEGALLY PRIVILEGED and which is
> intended only for the use of the individual or entity named above. If the
> reader of the e-mail is not the intended recipient or the employee or agent
> responsible for delivering it to the intended recipient, you are hereby
> notified that you are in possession of confidential and privileged
> information. Any unauthorized use, disclosure, copying or the taking of any
> action in reliance on the contents of this information is strictly
> prohibited and may be unlawful. If you have received this e-mail
> unintentionally, please immediately notify the sender via telephone at (773)
> 406-2464 or email.
>
>
> On Fri, Apr 27, 2012 at 6:43 AM, Richard Morris
> <
[log in to unmask]> wrote:
>> Dear list,
>>
>> I've noticed a change in the one-sample t-test design matrices produced by SPM8 compared to SPM5. I seem to remember SPM5 used to (automagically?) include subject effects, with columns for each subject in the design matrix, but SPM8 doesn't do that anymore.
Is there a setting change I can make to reintroduce subject effects in my design matrix?
>>
>> On a related note, is there any reason not to include the global covariate (ANCOVA) in a one-sample t-test of fMRI data? I've noticed I often get more regionally specific activation with higher t-values in my results when I include the global covariate.
I'm guessing this is because of subject-specific effects which I would like to remove/minimise.
>>
>> Best,
>>
>> Rich