Thank you Gary. On the first solution, I imagine I would have to specify
which 25 of the 50 treated units to find matches for? And on the second
solution, since I am designing the survey I do not yet have an outcome to
measure. The MakeFrontier() function call requires an outcome to run. Is
there some workaround or is my thinking mistaken?
On Tue, Jan 3, 2017 at 8:55 AM, Gary King <king(a)harvard.edu> wrote:
Hi Juan, You could ask matchit for the lowest
imbalance on a "greedy"
basis, say 25 treated units with the closest controls or some such.
Alternatively, if you add one component -- a specific overall imbalance
metric -- you have a well defined mathematical problem. To rephrase, you'd
like the subset with 25 treated and 25 (or more) controls that has the
lowest level of imbalance among the (huge number of) all possible such
subsets. If so, this paper <http://j.mp/1dRDMrE> on the matching balance
frontier can calculate this.
Best of luck with your research,
Gary
--
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IQSS <http://iq.harvard.edu/> - Harvard University
GaryKing.org - King(a)Harvard.edu - @KingGary <https://twitter.com/kinggary> -
617-500-7570 <(617)%20500-7570> - Assistant <king-assist(a)iq.harvard.edu>du>:
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On Tue, Jan 3, 2017 at 9:26 PM, Juan Tellez <juan.f.tellez(a)gmail.com>
wrote:
Hello,
I am planning a survey where I have 50ish treated municipalities and
hundreds to choose from as potential controls. The tricky part of this
matching exercise is that the survey will, in the end, only sample 25 of
the 50 treated municipalities. I don't particularly care which 25 of the 50
are chosen; what I am effectively looking for is the top 25
treatment-control pairs from my sample.
Is it possible to do this in MatchIt with a distance measure
like mahalanobis? The MatchIt package is understandably conservative about
discarding treatment observations, and when I use it to match I generally
end up with around 50 matched treated units. How might I go about this?
Thank you.
--
Best,
Juan Fernando Tellez
PhD Candidate
Department of Political Science
Duke University
--
Best,
Juan Fernando Tellez
PhD Candidate
Department of Political Science
Duke University