Hello,
Many thanks for your reply.
I am actually concerned about outliers in the timeseries used to compute %
signal change. Is there any easy way to (1) check whether outliers exist, and
(2) remove them?
Thanks again,
Lara
On Wed, 25 Mar 2009 13:15:00 +0000, Steve Smith
<[log in to unmask]> wrote:
>Hi,
>
>On 24 Mar 2009, at 19:39, Lara Foland wrote:
>
>> Hello,
>>
>> I'm using featquery to extract % signal change from each of my
>> subjects using
>> anatomical ROIs and a cope image. I have two questions:
>>
>> 1. Some of my subjects are showing a negative percent signal change.
>> I am
>> concerned that outliers may be causing this (atleast in part). Is
>> there any
>> easy way to check whether this may be the case?
>
>Do you mean outlier values within the ROI or outlier subjects? If you
>mean the former then you could just use alternative measures from the
>Featquery output results table, such as median.
>
>>
>> 2. If I apply a threshold of "0", does this mean that, foreach
>> timepoint where
>> % signal change is calculated to be negative, the % signal change is
>> set
>> to "0"?
>
>I think so, yes.
>
>Cheers.
>
>
>>
>> many thanks in advance for the help!
>> Lara
>>
>
>
>--------------------------------------------------------------------------
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>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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