- ... deviation1
- Note that in the simplest cases
the variance of the mean is the variance of the residuals divided by
the number of data points.
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- ... pooling2
- The first factor of in FV comes
from taking the mean of the first-level variances, i.e., pooling them,
and the second factor comes from converting this higher level variance
from a variance of residuals into the variance of the (higher-level)
mean. For more detail see [16].
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- ... mixed-effects3
- Note that the terms ``mixed effects''
and ``random effects'' are often (incorrectly) used interchangeably.
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- ... FE4
- We are attempting to identify
voxels of potential interest in ME-Z images; given that ME-Z can be
thought of as being related to FE-Z but scaled down by a factor
related to session variance, this seems like a good way of choosing
voxels which have the potential to be activated in the ME-Z image,
depending on the session variance. In order to investigate the
dependency of this approach on the FE-Z threshold chosen, we re-ran
the tests leading to the ME-Z plots presented in Figure 8,
having determined the regions of interest using a lower FE-Z threshold
(Z1.64, i.e., a factor of 5 more liberal in the significance
level). The mean ME-Z results were all scaled down, as expected, but
the qualitative (i.e., relative) results were exactly identical to
those presented in Figure 8.
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- ... above).5
- Whilst we are primarily investigating analysis efficiency and session
variance by looking at regions of potential activation, note that it
is also necessary to ensure that the non-activation (null) part of the
ME distribution is valid, i.e., not producing ``incorrect'' numbers of
false-positives; this investigation/correction of the ME null
distribution is addressed below and uses the whole ME-Z image, not
just the regions of potential activation.
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- ...
variability.6
- Noting the much greater variability (across
methods) in these ratios than in the plots in figure 8,
and by looking in detail at separate ME and FE variances, it is clear
that the variation in these figures across methods is primarily due to
variation in FE variance. This is possibly caused by differences in
the methods of correcting for temporal autocorrelation at first
level.
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