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From |
"Garrido, Melissa" <melissa.garrido@mssm.edu> |

To |
<statalist@hsphsun2.harvard.edu> |

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

Date |
Mon, 23 Aug 2010 12:59:29 -0400 |

Thank you, Maarten; that helped a lot. Melissa ________________________ 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 -------------------------- -----Original Message----- From: Garrido, Melissa Sent: Monday, August 23, 2010 10:14 AM To: 'statalist@hsphsun2.harvard.edu' Subject: Conditional marginal effects in heckprob Hi - 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(*) *** Thank you, Melissa -------------------------------------------------------------------- Melissa Garrido, PhD Research Health Science Specialist GRECC/REAP, James J Peters VA Medical Center 130 West Kingsbridge Road Bronx, NY 10468 718-584-9000 x 3804 melissa.garrido@va.gov Assistant Professor Department of Geriatrics & Palliative Medicine Box 1070 Mount Sinai School of Medicine One Gustave L. Levy Place New York, NY 10029 melissa.garrido@mssm.edu * * 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/

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