Hello-
I would like to know how to properly account for within-pair variance
correlation in FEAT in a twin design. We have measured a continuous
variable for all subjects that we are using as a regressor in our fMRI
analysis, but we recognize that this variable may not have error that is
independent of the twin-pair sampling. In our behavioral analysis in
STATA, we can easily implement a design that cluster/nests the twin
pairs to obtain robust standard errors. For the neuroimaging analysis,
the path is not so clear. I have the following questions:
1) We believe that FLAME 2's full MCMC resampling would automatically
produce robust standard errors in this case, but we would like to save
time by just running FLAME 1. Does the Metropolis Hastings sampling
procedure also result in robust standard errors in this case?
2) At the higher-level, would indicating separate Group membership in
FEAT's GLM setup (i.e. Inputs 1&2=Group 1, Inputs 2&3=Group 2, etc) be
the same as clustering twin pairs?
Thanks for everything,
--
Jim Porter
TRiCAM Lab Coordinator
Elliott Hall N437
612.624.3892
www.psych.umn.edu/research/tricam
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