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st: R: stpiece - general hazard estimation question


From   "Carlo Lazzaro" <carlo.lazzaro@tiscalinet.it>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: R: stpiece - general hazard estimation question
Date   Fri, 31 Jul 2009 08:03:27 +0200

Steven wrote: 

<In my first time period for my firms, I have no exits so the hazard
coefficient is very low.  Unfortunately, because there are no exits it also
indicates it is non-significant. (p=.969).>

At first glance, this result would seem consistent with your data generating
process: no exits mean very low hazard and very high p-value. Probably, the
best solution here is try to explain (eg. according to the economic theory
or taking a look at previous researches in the same field) why this result
is or is not reasonable.

<Given there are no standard errors if there is not an exit..>

This statement seems a little bewildering, as you actually reported a
standard error for TP1 (528.1418).

HTH and Kind Regards,
Carlo

-----Messaggio originale-----
Da: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Per conto di Bradley, Steve
Inviato: giovedì 30 luglio 2009 23.54
A: 'statalist@hsphsun2.harvard.edu'
Oggetto: st: stpiece - general hazard estimation question

Statlisters,

I have a question regarding the estimation of hazards when there isn't one
for a particular time period.  In my first time period for my firms, I have
no exits so the hazard coefficient is very low.  Unfortunately, because
there are no exits it also indicates it is non-significant. (p=.969).

						
_t	Coef.		Std. Err.	z	P>z

TP1	-20.66249	528.1418	-0.04	0.969	
TP2	-5.362681	.8858187	-6.05	0.000	
TP3	-5.62141	.7207315	-7.80	0.000		


As an experiment, if I add one firm exit during time period 1 to confirm
this is an estimation problem I get:

          _t |      Coef.   Std. Err.      z    P>|z|     [95% Conf.
Interval]
-------------+--------------------------------------------------------------
--
  TP1		 |  -7.638006   1.206193    -6.33   0.000     -10.0021
-5.273911
  TP2 	 |  -4.855396    .782516    -6.20   0.000      -6.3891   -3.321693
  TP3		 |   -5.48794    .711463    -7.71   0.000    -6.882382
-4.093498
          

I am wondering if there is an appropriate solution to this problem.  Given
there are no standard errors if there is not an exit, can I consider the
standard error 0 and use the original coefficient or is it unreliable as
well?

Thanks!


Steven W. Bradley, Ph.D.
Department of Management & Entrepreneurship
One Bear Place #98006
Baylor University
Waco, TX  76798
(office) 254.710.3921
steve_bradley@baylor.edu



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