Statalist


[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

Re: st: Krinsky and Robb procedure


From   German Muchnik Izon <german@unm.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Krinsky and Robb procedure
Date   Mon, 25 Aug 2008 08:33:04 -0600

Dear Martin,

Thank you so much for your suggestion. It works!!
Now I am going to see if I can program a convolution 
approach in stata to see if the median WTP I get for the 
two goods I included in my survey are statistically 
different from each other.

Best,
German.

-----------------------------
Germán M. Izón
Department of Economics
PhD. Candidate
The University of New Mexico
Ph# (505) 277-1951

--- On Sat, 8/23/08, Martin Weiss 
<martin.weiss@uni-tuebingen.de> wrote:

     From: Martin Weiss <martin.weiss@uni-tuebingen.de>
     Subject: Re: st: Krinsky and Robb procedure
     To: statalist@hsphsun2.harvard.edu
     Date: Saturday, August 23, 2008, 11:45 AM

     Let me try an answer: if you look at the code of 
wtpcikr.ado, it calls
     -simulate- in line 57, saving into a -tempfile- with 
the option
     -saving(`simdat')-. I was able to turn this 
-tempfile- into a
     permanent one by appending the following after line 
134 (and saving
     wtpcikr.ado under a different name (wtpcikr2.ado)):


     ***********
       u `simdat', clear
       save mysimdat
     ***********

     This will allow you to access the meanwtp and the 
medianwtp from each
     simulation run
      afterwards.

     HTH
     Martin





     Quoting German Muchnik Izon <german@unm.edu>:

     > Hi all,
     >
     > I have a new question. I am estimating 95% 
confidence
     > intervals for willingness to pay (WTP) for a good 
using a
     > command called wtpcikr that implements the Krinsky 
and
     > Robb procedure, recently developed by P. Wilner 
Jeanty for
     > stata. Based on a power point presentation given by 
Jeanty
     > at the 6th North American Stata Users Group Meeting 
2007,
     > the steps of this procedure is as follows:
     >
     > 1.Estimate the WTP model of interest
     > 2.Obtain the vector of parameter estimates     and 
the
     > variance-covariance (VCV) matrix
     > 3.Calculate the Cholesky decomposition, C, of the 
VCV
     > matrix such that
     > 4.Randomly draw from standard normal distribution a 
vector
     > x with k independent elements
     > 5.Calculate a new parameter
      vector Z such that
     > 6.Use the new parameter vector Z to calculate the 
WTP
     > measures of interest
     > 7.Repeat steps 4, 5, and 6 N(>=5000) times to 
obtain an
     > empirical distribution of WTP
     > 8.Sort the N values of the WTP function in 
ascending order
     > 9.Obtain a 95% confidence interval around 
mean/median by
     > dropping the top and bottom 2.5% of the 
observations
     >
     > The example given in this presentation is:
     >
     > drop _all
     > . set memory 8m
     > . use south
     > . gen lbid=ln(bid)
     > . probit ypay lbid unlimwat govtpur environ 
waterbill
     > urban
     > . wtpcikr lbid unlimwat govtpur environ waterbill 
urban,
     > reps(50000) meanl expo
     >
     >
     > Is there a way in stata to obtain a vector of the 
mean
     > WTP's that are estimated in step 6 after each 
replication.
     >
     > Thank you!!
     >
     > German.
     >
     > *
     > *   For
      searches and help try:
     > *   http://www.stata.com/help.cgi?search
     > *   http://www.stata.com/support/statalist/faq
     > *   http://www.ats.ucla.edu/stat/stata/
     >




     *
     *   For searches and help try:
     *   http://www.stata.com/help.cgi?search
     *   http://www.stata.com/support/statalist/faq
     *   http://www.ats.ucla.edu/stat/stata/


*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index