Its not entirely clear what you're doing, but the best way to do this
kind of thing is to figure out the ONE quantity of interest. In your
case, maybe that's the difference in the differences? Whatever model
you would choose you would then compute 2 first differences and take the
difference between those. you can compute the standard error of this
quantity of using all the simulations of this difference in differences.
Gary
---
http://gking.harvard.edu
Donald Braman wrote:
I'm wondering if there is a simple way to use
Zelig to compare changes
in the differences between two groups across conditions. I have two
groups, I can easily determine that the difference between them in
condition1 is signfiicant and also that the difference between them in
condition2 is significant. But I am wondering wether the change in
the difference is signfiicant -- that is, does the change from
condition1 to condition2 make them significantly more or less alike?
Donald Braman
http://www.law.gwu.edu/Faculty/profile.aspx?id=10123
http://research.yale.edu/culturalcognition
http://ssrn.com/author=286206
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