st: permutation, strata() for empirical statistic distributions

[David Airey <david.airey@vanderbilt.edu>]

If you have a model, and you wish to determine the multiple test 
probability for your data set, you can use a multiple test correction 
procedure, or you can permute the data set many times to get an 
empirical distribution of test statistics.

(1) I'm assuming if the data is grouped or stratified, the permutation 
procedure should respect that. So if student|class|school, then you 
don't want to permute the student into a class he was never in. I see 
an option in permute that is "strata". Does this serve this purpose?

(2) A permutation procedure that respects nesting, should have a model 
that respects nesting. That is, it makes no sense to respect the 
nesting in the permutation procedure, but then ignore strata in the 
model, right?

Thanks,

Dave

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