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Re: st: Verify randomization in a large sample


From   "Austin Nichols" <austinnichols@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Verify randomization in a large sample
Date   Tue, 30 Sep 2008 22:04:59 -0400

José Luis Chávez Calva <josechc@gmail.com>:
The only way to verify randomization is to observe the randomization
mechanism.  But you can check the balance by comparing means of
several variables in the dataset like age, gender, language, etc.
across categories.  For example, if you have treatment and control
groups defined by a variable t (=0 for control and =1 for treatment),
you can do
 hotelling age gender language etc, by(t)
or
 reg t age gender language etc
to get an F test of the null that all means are the same.  Assuming
variances may differ, you can
 reg t age gender language etc, r
and for alternative models you can run logit or probit instead (to get
a chi2 test).  Presumably, for a categorical t you could run
 mlogit t age gender language etc
or -mprobit- assuming a specific error distribution under the null of
randomization (in which case the X vars should not help you predict
t).  All of that is just for comparisons of means; for higher moments
you will need tests of equality of distributions (e.g. -ksmirnov-) or
graphical methods (e.g. -qqplot-).

On Tue, Sep 30, 2008 at 8:18 PM, José Luis Chávez Calva
<josechc@gmail.com> wrote:
> Dear Stata users:
>
> I have a dataset on household income with a large number of
> individuals. The set contains one variable indicating the locality
> where each individual lives and another one indicating the household
> to which this individual belongs to. I would like to know how to
> verify randomization both at locality and household level using
> several variables in the dataset like age, gender, language, etc.

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