Dear Clare,
At 10:19 04/10/99 +0100, Clare E. Mackay wrote:
| Is the T statistic map scaled then? ie what does the value of 256 in
| Analyze correspond to in the T map? The maximum T in the analysis?
The SPM written from the "write-filtered" button is scaled. The scalefactor
is in the Analyze header. Look at spm_format.man for a definition of the
Analyze header used by SPM, spm_vol.m for a simple way to extract the scale
factor, or see http://www.mrc-cbu.cam.ac.uk/Imaging/analyze_fmt.htm
-andrew
| On Fri, 1 Oct 1999, Karl Friston wrote:
| > Clare Mackay wrote:
| > > The next question is: When you output the results using 'write
| > > filtered', is the maximum value always 8.21, or is it scaled
| > > depending upon the maximum Z value of your data set?
| >
| > In SPM99 the values written are actually the statistic (e.g. T or F),
| > not the Z equivalent score. The Z equivalent Ze is computed such that
| >
| > p(t > T) = p(Z > Ze)
| >
| > and only appears in the tables for reporting maxima in papers.
| > There is no upper limit on these statistics.
+ - Dr Andrew Holmes mailto:[log in to unmask]
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