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

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Conditional marginal effects in heckprob |

Date |
Mon, 23 Aug 2010 14:44:40 +0000 (GMT) |

--- On Mon, 23/8/10, Garrido, Melissa wrote: > I have a question about the -margins- command in Stata 11, > when used after heckprob. > > > I want to get conditional marginal effects of my outcome > variable, but I'm not sure whether I have the correct > syntax (and haven't found the answer in the help files). > > Is the default option within -margins- to calculate the > conditional marginal effect, or is there something > additional I need to specify? > > Here is what I have: > > **** > > heckprob diedvsroutinetotal = $indepvar , select > (not_transfer = $indepvar $instruments) > > /*Marginal effects at means:*/ > > margins, dydx(*) atmeans > > > /*Average marginal effect:*/ > > margins, dydx(*) I assume that with conditional marginal effects you mean the marginal effect on the predicted probability of success conditional on selection. In that case you need to add the -predict(pcond)- option. Right now, you are estimating the marginal effect on probability of success. The -predict()- option in -margins- determines what your response/dependent/explained/y variable is, and if you do not specify it, it will assume that it is the default for -predict-. If you look at -help heckprob postestimation-, you will see that the default is -pmargin-, which is described as "the default, calculates the univariate (marginal) predicted probability of success; Pr(depvar=1)" You probably want: "pcond calculates the conditional (on selection) predicted probability of success; Pr(depvar=1 | depvar_s=1) = Pr(depvar=1, depvar_s=1)/Pr(depvar_s=1)." Hope this helps, 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**:**st: may not use noninteger frequency weights***From:*Kiss Sándor Csanád <kiss.sandor.csanad@mkkt.hu>

**References**:**st: Conditional marginal effects in heckprob***From:*"Garrido, Melissa" <melissa.garrido@mssm.edu>

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