Sure - you would 'just' need an "alternate hypothesis" to disprove.
For example, the mixture modelling tool in FSL would tell you the
relative probability of null vs. alternate.
Cheers.
On 19 Mar 2009, at 13:16, Daniel CM wrote:
> Cool. Thanks. Very true. Last that I knew of, there is no explicit
> test that the two groups are the same.... is there?
>
>
> Steve Smith wrote:
>> Hi - yes, that seems right I think - though note that strictly
>> speaking statistically, finding no significant group difference is
>> not the same as an explicit test that the null is true....
>> Cheers.
>>
>>
>> On 18 Mar 2009, at 12:59, Daniel CM wrote:
>>
>>> Hi I just wanted to check that we are doing the correct thing
>>> here...
>>>
>>> We scanned an initial group of subjects on an fMRI task and we
>>> realised that
>>> there was a problem with the aquisition sequence. So, we scanned
>>> a new
>>> group of subjects again, a few months later. Of course, we wanted
>>> to see if
>>> we could still use the original subjects. Our strategy was as
>>> follows:
>>>
>>> Place all the lower level feats into a higher-level analysis as
>>> two groups, in
>>> two columns as outlined in the Feat manual. [# #]. Then check for
>>> differences between the groups [1 -1] and [-1 1] on each
>>> contrast. Since
>>> there were no major differences, but still thinking it is safer
>>> treat these groups
>>> as having different variances, we then wanted to know the COPE for
>>> both
>>> groups combined. So, we simply set the higher level contrast as [1
>>> 1].
>>>
>>> Does this sound about right?
>>>
>>> Cheers,
>>> Dan CM
>>>
>>
>>
>> ---------------------------------------------------------------------------
>> Stephen M. Smith, Professor of Biomedical Engineering
>> Associate Director, Oxford University FMRIB Centre
>>
>> FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
>> +44 (0) 1865 222726 (fax 222717)
>> [log in to unmask] http://www.fmrib.ox.ac.uk/~steve
>> ---------------------------------------------------------------------------
>>
>
---------------------------------------------------------------------------
Stephen M. Smith, Professor of Biomedical Engineering
Associate Director, Oxford University FMRIB Centre
FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
---------------------------------------------------------------------------
|