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From |
Maarten buis <maartenbuis@yahoo.co.uk> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Re: what is the difference between '.psel' and '.xbs' for heckman postestimation |

Date |
Wed, 21 Apr 2010 07:37:23 +0000 (GMT) |

--- On Wed, 21/4/10, jing liu wrote: > but now I don't understand if -twostep- in heckman > regression doesn't work with any weight command, > then why there is no error message coming up when > i put them together. And it seems -twostep- works > with weights command, because there are some > outputs showed later, although now i am doubting > if they are correct. I am able to reproduce this inconsistency between what the help-file says and what -heckman- does. I would stick with what the help file says until StataCorp says it is OK to use weights in combination witht he -twostep- option. My guess is that the weights are just ignored in that case. The reason for this belief is that in the example below I specified -pweights-, which automatically implies that the resulting standard errors should be robust standard errors, but this is not the case. *-------------- begin example -------------- webuse womenwk gen w = runiform() heckman wage educ age [pw=w], twostep /// select(married children educ age) *------------- end example ----------------- -- Maarten -------------------------- Maarten L. Buis Institut fuer Soziologie Universitaet Tuebingen Wilhelmstrasse 36 72074 Tuebingen Germany http://www.maartenbuis.nl -------------------------- * * 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/

**Follow-Ups**:**Re: st: Re: what is the difference between '.psel' and '.xbs' for heckman postestimation***From:*"Brian P. Poi" <bpoi@stata.com>

**Re: st: Re: what is the difference between '.psel' and '.xbs' for heckman postestimation***From:*jing liu <pku.liujing@gmail.com>

**References**:**Re: st: Re: what is the difference between '.psel' and '.xbs' for heckman postestimation***From:*jing liu <pku.liujing@gmail.com>

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