Dear SPM:
some simple questions.
When specifying stochastic designs there is a question about event
probability. Assuming 3 events with equal probabilities is
1/3 1/3 1/3 the same as 1 1 1 for practical purposes?
Let's say I specify a design with 2 trial types and a null event. The xX.X
matrix is n x 3 columns, with column 3 being all 1's.
Would the efficiency of this design be approximated by
trace(xX.X(:,1:2)*xX.X(:,1:2)')-1 ??
Have you found it useful to estimate designs repeatedly to get one that is
more efficient?
thanks,
darren
Darren R. Gitelman, M.D.
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