Dear SPM list,
So far I've had no replies yet to my question outlined below and I have no
idea how to solve this problem.
I still do not seem to be able to perform RFX 2-sample t-tests in spm2 anymore.
If anybody has ideas concerning things I could try to (hopefully) solve this
problem, I would be extremely greatful.
I don't know if it's relevant here, but I'm using spm2 with Matlab (tried
both R13 and R14) on a Windows 2000 PC.
Many thanks in advance,
Bianca de Haan
On Fri, 18 Jan 2008 16:30:00 +0000, B. de Haan
<[log in to unmask]> wrote:
>The problem described below persists (I have no also reproduced the same
>error on every computer I could get my hands on), however, I have managed to
>narrow the potential source of the problem down a bit:
>
>The 2-sample t-test aims to compare group 1 (10 first level .con images)
>with group 2 (10 first level .con images).
>
>When I run this second level 2-sample t-test it produces valid looking beta
>images for both groups (beta1 for group1 and beta2 for group2). The produced
>con image also looks good and corresponds to the difference between beta1
>and beta2. The resMS image also looks believable. However, the spmT image
>produced from the comparison of the con image to the resMS image contains
>only the value 0, which should not be possible.
>
>Hopefully this additional information will allow someone to find out what
>goes wrong here.... Unfortunately it is very important that I get this
>2-sample t-test to work again on spm2.
>
>Many thanks in advance,
>
>Bianca de Haan
>
>
>
>On Thu, 17 Jan 2008 18:29:33 +0000, B. de Haan
><[log in to unmask]> wrote:
>
>>Dear SPM-list,
>>
>>I am having some problems when trying to reanalyze old data with spm2:
>>
>>two-sample t-tests between two groups suddenly seem to produce only empty
>>spmT images (the whole spmT_000x image is 0). I've been using spm2 for years
>>and have never encountered this problem.
>>
>>
>>1) This problem is specific to two-sample t-tests between the 2 groups;
>>one-sample t-tests in spm2 on each of the 2 groups work fine and produce the
>>same results they did a year ago.
>>
>>2) This problem is also specific to spm2; the same two-sample t-test between
>>the 2 groups using spm5 works fine and produces the same results as I got a
>>year ago with spm2.
>>
>>3) 2-group ANOVA in spm2 (should produce the same results as 2-sample
>>t-test) again only produces empty spmT images.
>>
>>4) I have re-downloaded and installed spm2 and tried the two-sample t-test
>>on both Matlab6.5 and Matlab7.1. All to no avail.
>>
>>5) The 2-sample t-test design matrix from the current analysis looks
>>radically different from the design matrix from the analysis I performed a
>>year ago and I do not seem to be able to reproduce the design matrix from a
>>year ago in spm2 anymore (I tried every combination of the 2-sample t-test
>>settings possible). However, as mentioned above, if I do the same 2-sample
>>t-test in spm5, I obtain the same results as I did a year ago again,
>>therefore I feel confident that my 'old' results are valid.
>>
>>
>>I am pretty much at my wits end as to why I no longer can perform 2-sample
>>t-tests in spm2. I would really like to stick with spm2 for this old dataset
>>(am just trying to do a few small additional analyses in response to
>>reviewer's comments). Does anybody have any idea what might be going on here
>>and how to solve this?
>>
>>Many thanks in advance,
>>
>>Bianca de Haan
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