Thanks again.

OK. I just want to make triple sure.

In MRI 1
Subjects either attended to the breath or were at rest. I have an average effect with two contrasts and an EV for 15 subjects.

Intervention= meditation training

In MRI 2 (after training)

Subjects either meditated to breath or were at rest. I have an average effect with two contrasts and an EV for 15 subjects.

I then took the two group “copes” from each MRI session and compared with two contrasts and 1 EV.

I can’t do this? If not, how would you got about comparing these sessions?

THANK YOU SO MUCH FOR YOUR TIME.

Sincerely,
Fadel

On 5/19/11 12:51 PM, "Eugene Duff" <[log in to unmask]> wrote:

Hi Fadel -

So you mean a model with just the two group means as inputs, modelling the differences?  Or just subtracting the copes? No these aren't appropriate approaches.

Cheers,

Eugene


On 19 May 2011 17:28, Fadel Zeidan <[log in to unmask]> wrote:
Hi.

Thanks for your response.

My main question is, can I compare to higher level analyses in a within subjects fashion.

I have a group average for Time 1 before an intervention and another for after the intervention.

I want compare them directly and I have by simply comparing their respective copes in FEAT. Can this be justified without being too liberal in my stats?

Thanks so much!


On 5/19/11 12:10 PM, "Eugene Duff" <[log in to unmask]> wrote:

Hi Fadel -

Are you saying your a comparing paired and unpaired t-tests?  I suspect there is something wrong with the model if the paired t-test images are coming out speckled.

Eugene

On 19 May 2011 16:16, Fadel <[log in to unmask]> wrote:
Simply put: Can I compare to third level analyses in a within subjects fashion.

There were two conditions in MRI session 1. Subjects performed a task (manipulation) and did not (rest).
I have the group effect for these contrasts corresponding to MRI 1.

Subjects then participated in an intervention.


There were two conditions in MRI session 2 (after the intervention). Subjects performed a task (manipulation) and did not (rest).
I have the group effect for these contrasts corresponding to MRI 2.

Am I being too liberal? Am I treating within subject variability as between subject variability? The analysis comes out beautifully. I also ran a paired-t test with the same data, and the images come out speckled. I've checked for outliers and have reran the analyses dozens of times to no avail.

Thanks.