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RE: st: Defining observation specific truncation points with truncreg


From   Eric Sevigny <els21+@pitt.edu>
To   statalist@hsphsun2.harvard.edu
Subject   RE: st: Defining observation specific truncation points with truncreg
Date   Fri, 01 Oct 2004 10:17:53 -0400

This was helpful. Thanks! In hindsight, the answer to my question was kind of intuitive. Just code the truncation value into trunc for each stratification of interest (in my case year). For some reason, this solution eluded me as I was formulating my analyses. Thanks again.

Eric

--On Thursday, September 30, 2004 10:29 PM -0500 Scott Merryman <smerryman@kc.rr.com> wrote:r


Suppose, in the auto dataset, domestic observations are truncated at 17
while foreign observations are truncated at 18. I believe you could do the
following:


. sysuse auto
(1978 Automobile Data)

. gen trunc = cond(foreign == 0,17, 18)

. truncreg mpg price, ll(trunc) nolog
(note: 20 obs. truncated)

Truncated regression
Limit:   lower =      trunc                             Number of obs =
54
         upper =       +inf                             Wald chi2(1)  =
0.62
Log likelihood = -150.79259                             Prob > chi2   =
0.4312

-------------------------------------------------------------------------
--- --
         mpg |      Coef.   Std. Err.      z    P>|z|     [95% Conf.
Interval]
-------------+-----------------------------------------------------------
--- --
eq1          |
       price |  -.0015613   .0019834    -0.79   0.431    -.0054486
.0023261
       _cons |    19.6171   10.84309     1.81   0.070    -1.634962
40.86917
-------------+-----------------------------------------------------------
--- --
sigma        |
       _cons |   9.881807   3.537671     2.79   0.005       2.9481
16.81551
-------------------------------------------------------------------------
--- --

Hope this helps,
Scott

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-
statalist@hsphsun2.harvard.edu] On Behalf Of Eric Sevigny
Sent: Thursday, September 30, 2004 5:07 PM
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: Defining observation specific truncation points with
truncreg

Right, but what if I have ll(10) for 1997 and ll(20) for 1996 and want to
model these different truncation points? Can I do that with truncreg?

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