On Wed, Nov 3, 2010 at 7:40 AM, Prashant <presearchwork@gmail.com> wrote:

Hi,

I was wondering if I could use coarsened exact matching (CEM) to
create the following type of blocks/strata for a randomized
experiment:

1st stage: block 50 schools into pairs (25 pairs total), randomization
would take place in each pair
2nd stage: Take the students in each of the above schools (say there
are 60 students in each school) and stratify them into triples as
well, randomization would take place within each triple (assigned to
treatment A, treatment B, and control).

I have read for example that the cem command in Stata can create
blocks for a randomized experiment, but I am not sure if it can create
matched pairs and triples as in the above situation or not, since CEM
may create different size blocks/strata according to the variables and
degree of coarsening one chooses, rather than creating pairs/triples
per say -- is there a way to actually create pairs/triples using CEM
or do I have to additionally rely on another matching method (say
using some distance measure) to create pairs/triples? And is further
creating pairs/triples (beyond the blocks from cem) necessarily
helpful in reducing bias and increasing power?

Thank you so much in advance for your help,
Prashant

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