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From |
Martin Weiss <martin.weiss@uni-tuebingen.de> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Krinsky and Robb procedure |

Date |
Sat, 23 Aug 2008 18:45:29 +0200 |

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/

**References**:**st: Krinsky and Robb procedure***From:*German Muchnik Izon <german@unm.edu>

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