Matt,

Thanks for the response, that helps.  It does generate a couple of follow-up questions:

First, in Stata, does the "cem" command work the same way as the "imb" command in calculating the multivariate L1 distance?  Is there an option under the "breaks()" argument that I can specify where I can be sure it is using the user-specified cutoff points?

Second, I'm not sure if I understand your point about using different cutoff points to measure imbalance than the ones used in the matching.
I thought that one of the benefits of CEM was that the user could up front declare how much imbalance they are willing to tolerate by coarsening the variables as he/she saw fit.  Assuming the researcher is coarsening the variables with sound reasons, why not use those same cutoff points to measure imbalance?
One of the examples that you and your colleagues have used is coarsening a 'years of education' variable.
If the researcher coarsens that variable in meaningful ways for matching (0-8; 9-12; 12-16; >16), and then measures imbalance using the scott or sturges break method where the cutpoints are changed to non-meaningful cutpoints (5.5; 7.5; 9.5; 11.5; etc), I'm unclear as to how that calculated L1 distance would be more valid than calculating the L1 distance with the user-set cutoff points.

Any clarification would be greatly appreciated and thanks for your time.

Evan
   


On Tue, Feb 5, 2013 at 8:53 AM, Matt Blackwell <m.blackwell@rochester.edu> wrote:
Hi Evan, 

There's currently no way to set variable-specific cut points for the "imb" command. You can only change the algorithm for all variables via the "breaks()" argument. For the imb command, it's best to use a set of cut points other than the ones you use for the matching and keep that cut point fixed while you attempt different matching solutions. 

Hope that helps!

Cheers,
matt.


On Fri, Feb 1, 2013 at 1:13 PM, Evan Cole <cole.s.evan@gmail.com> wrote:
CEM Users,

When using Stata and the imb command, is their anyway to change it so that it recognizes user-defined cutpoints to calculate the L1 distance instead of defaulting to the scott method?
I have tried running the imb command after a cem command with user defined cutpoints but it still uses the scott method.
Any help would be greatly appreciated.  Thanks for the time.

Evan Cole
Tulane University  

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