Does that mean that if I have more than one EV, I cannot contrast a single
EV to baseline (i.e. my fixation condition)? For example, I have:
Task - Control [1 -1]
Control - Task [-1 1]
Task - Fixation [1 0]
Control - Fixation [0 1]
All - Fixation [1 1]
Are the last three contrasts wrong? Assuming they are correctly set up, I
would think that something like "Task - Fixation [1 0]" would contrast task
to both fixation (baseline) and control. I'm sure I'm misunderstanding this.
Could anyone clarify it for me?
Thanks a bunch,
Lin
On Fri, 23 Jan 2009 07:23:34 +0000, Steve Smith <[log in to unmask]> wrote:
>If you have two tasks, i.e. "task" and "control" then yes you put them
>as two EVs, and contrast them with (e.g.) [1 -1].
>If you have just one task, and want to compare that to baseline, then
>you have one EV, and contrast the task with baseline using [1]
>Steve.
>
>
>
>
>On 22 Jan 2009, at 22:02, Lin Nga wrote:
>
>> Hi everyone,
>>
>> Sorry if I'm treading old grounds here but it isn't exactly clear to
>> me how
>> FSL compares the EVs to fixation condition if it isn't explicitly
>> set as an
>> EV. For example if there are two EV's, task and control, I know that
>> if I
>> wanted to contrast task to fixation I would use [1 0]. Wouldn't task
>> be
>> contrasted to both control and fixation in this case, since control
>> is set to 0?
>>
>> Thanks again,
>> Lin
>>
>
>
>---------------------------------------------------------------------------
>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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