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
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>
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