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From |
lutunnahar begum <pikitardif@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: How to get marginal effect of quadratic term in tobit model in stata 11.0 |

Date |
Tue, 19 Jul 2011 09:05:47 +1000 |

Hi Maarten Thanks...that's really a good way to see the non-linear effect. I will definitely try that. I tried the following command: gen tb2=tb^2 tobit ch tb tb2 .........., ll(0) robust margins, dydx(*) predict (ystar (0,.)) post I also tried -dtobit- with -version 8.2- and got the 4 MEs for squared term. I understand that the true ME should not consider the squared effect separately as there is only one variable. But papers using tobit model report the marginal effect of squared term. I am confused whether I should use the above mentioned command to get this. But what will be the interpretation? Thanks for your help. Regards, Nahar On Mon, Jul 18, 2011 at 9:18 PM, Maarten Buis <maartenlbuis@gmail.com> wrote: > On Mon, Jul 18, 2011 at 1:07 PM, lutunnahar begum wrote: >> I am using stata 11.0. I am interested in non-linear effect of some of >> the regressors in tobit model....but for tobit, we don't get any >> marginal effect for quadratic term. > > And that is exactly as it should be. Conceptually, adding a squared > term of a variable x only means that x has a non-linear effect. So > there is only one variable x. The fact that the the variable x is > entered in the model as two "variables", x and x^2, does not change > the fact that from a substantive point of view there is only one > variable. Maybe you find the following helpful: > > <http://www.maartenbuis.nl/publications/inter_quadr.html> > > 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/ > * * 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: How to get marginal effect of quadratic term in tobit model in stata 11.0***From:*Maarten Buis <maartenlbuis@gmail.com>

**References**:**st: How to get marginal effect of quadratic term in tobit model in stata 11.0***From:*lutunnahar begum <pikitardif@gmail.com>

**Re: st: How to get marginal effect of quadratic term in tobit model in stata 11.0***From:*Maarten Buis <maartenlbuis@gmail.com>

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