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Re: st: Matched ID in Kernel Matching (PSMATCH2)


From   Santosh Kumar <santosh.uh@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Matched ID in Kernel Matching (PSMATCH2)
Date   Fri, 24 Sep 2010 14:57:41 -0400

'
psmatch2 elec , pscore(p_score) outcome(tot_inc) common kernel
kerneltype(normal)
(58 missing values generated)

----------------------------------------------------------------------------------------
        Variable     Sample |    Treated     Controls   Difference
    S.E.   T-stat
----------------------------+-----------------------------------------------------------

         tot_inc  Unmatched | 26403.8163   21601.3601   4802.45621
2250.21202     2.13
                        ATT         | 25879.7292   21253.0151
4626.71401   2343.87751     1.97
----------------------------+-----------------------------------------------------------
Note: S.E. for ATT does not take into account that the propensity
score is estimated.
 psmatch2: |   psmatch2: Common
 Treatment |        support
assignment | Off suppo  On suppor |     Total
-----------+----------------------+----------
 Untreated |         0        761 |       761
   Treated |        20      1,259 |     1,279
-----------+----------------------+----------
     Total |        20      2,020 |     2,040

. pstest hhsize hhsizesq head_sex head_age hagesq   hh_marital1 hhlit
lit land landsq   dtap dbrick dreligion dcow dbull dhorse dpoultry
t_pop disdzonk,
>  sum
----------------------------------------------------------------------------
                        |       Mean               %reduct |     t-test
    Variable     Sample | Treated Control    %bias  |bias| |    t    p>|t|
------------------------+----------------------------------+----------------
      hhsize  Unmatched | 4.3339   4.4192     -4.1         |  -0.89  0.371
                Matched       | 4.3082   4.3847     -3.6    10.3 |  -0.93  0.350

Could anyone help in how to get the hhsize for control in the matched
sample (i.e. 4.3847)?
bysort _treated: su hhsize gives hhsize for treated and control for
unmatched sample.
bysort _treated: su hhsize if  _support==1 gives hhsize for treated in
matched sample.

But, I am struggling to figure out how the hhsize for control for
matched sample is generated?

Thanks,
Santosh

On Fri, Sep 24, 2010 at 1:02 PM, Austin Nichols <austinnichols@gmail.com> wrote:
> Santosh Kumar <santosh.uh@gmail.com>:
>
> Your -psmatch2- syntax is suspect, since you are not regressing a
> treatment indicator on controls.  That said...
> Why not reweight instead of match?
>
> la var t "Treatment"
> su t, mean
> loc m=r(mean)
> la var pvar "Estimated Propensity Score"
> g w=cond(t,`m'/(`-`m'),pvar/(1-pvar))
> la var w "ATT weight"
> logit y t x* [pw=w]
>
> Have you tried rerunning -psmatch2- multiple times to see if you get
> the same estimate every time?  My guess is that your estimate depends
> on the sort order of your data, which is an odd feature for any
> estimator.
>
>
> On Thu, Sep 23, 2010 at 12:38 PM, Santosh Kumar <santosh.uh@gmail.com> wrote:
>> Dear listserv,
>>
>> I want to use propensity score matching to match the treated with the
>> control. I am using Kernel matching. Instead of getting ATT, I want to
>> run a logistic regression on the matched sample. I am struggling to
>> create a matched sample in kernel matching. In nearest neighbor
>> matching, follwoing syntax will created a matched sample.
>>
>> psmatch2 xvar, pscore(pvar) outcome(yvar) caliper(.001) noreplace
>> neighbor(1)
>> gen pair = _id if _treated==0
>> replace pair = _n1 if _treated==1
>> bysort pair: egen paircount = count(pair)
>> drop if paircount !=2
>> save paired, replace
>>
>> Could anyone help me in creating a matched sample with Kernel Matching?
> *
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>



-- 

Santosh

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