Dear Peter,
> > I would say, with an air of casual authority, that 'it is generally
> > accepted that 12 subjects are sufficent to detect activations of 0.25%
> > (fMRI) or 4% (PET) at a specificiy of 95% and sufficient sensitivity to
> > detect at least one activated brain region' and then quote.....
>
> Are the corresponding figures for SPECT known?
I am afraid I do not know of specific details. In fact the above
response was a little specious so do not take it too seriously. In
general the sensitivity (i.e. power) is related to error variance,
design efficiency and the degrees of freedom of the study. The latter
are less in SPECT than in PET because you only have one or two
observations per subject. One might think that you would need more
subjects in SPECT as a result.
With best wishes - Karl
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